pigs in mud

The gut-brain axis in livestock animals: Is there a place for biotics in changing pig behavior?

By Prof. Seppo Salminen PhD, University of Turku, Finland

When pigs are kept as livestock, ‘manipulative behaviour’ is relatively common and it most often consists of biting, touching, or close contact with ears or tails of pen mates, without always resulting in visible wounds. Such pig behavior can cause stress and sometimes results in physical injuries. Chronic stress, nutritional deprivation, diet formulation, health problems, environmental discomfort, high stocking density and competition over resources are among the reported risk factors for tail biting in pigs. However, the precise factors behind behavioral problems in domesticated pigs remain poorly understood. It has been suggested that manipulative behavior may be associated with gut microbiota composition and activity via the gut-brain axis, with potential influence from the metabolites produced by gut microbes.

A multidisciplinary team of researchers recently assessed manipulative pig behaviour and gut microbiota interrelations (König et al. 2024). The aim was to identify pigs performing tail and/or ear manipulation (manipulator pigs) and to compare their fecal microbiota with that of control pigs not manifesting such behaviour. The study was conducted by analyzing video recordings of 45-day-old pigs. Altogether 15 manipulator-control pairs were identified (n = 30). Controls did not receive nor perform manipulative behaviour.

Rectal fecal samples of manipulators and controls were compared on two parameters: (1) culturable lactobacilli, and (2) microbiota composition. 16S PCR was used to identify Lactobacillaceae species after culture isolation, and 16S amplicon sequencing was used to determine fecal microbiota composition. The researchers found fewer culturable Lactobacillaceae species in fecal samples of pigs performing manipulative behaviour, with seven culturable Lactobacillaceae species identified in control pigs and four in manipulator pigs. Manipulators (p = 0.02) and female pigs (p = 0.005), however, expressed higher overall counts of Lactobacillus amylovorus, and the researchers found a significant interaction (sex * status: p = 0.005) with this sex difference being more marked in controls. Manipulator pigs tended to express higher total abundance of Lactobacillaceae but lower alpha diversity. A tendency for an interaction was seen in Limosilactobacillus reuteri (sex * status: p = 0.09). The results add to the findings of an earlier study reporting that intestinal microbiota was changed and lactobacilli were more abundant in a negative control group compared with biting pigs (Rabhi et al. 2020). Taken together, these studies suggest that specific lactobacilli  as well as low diversity of Lactobacillaceae may be factors impacting manipulative behavior.

Manipulative behavior is an important challenge in swine production as it impacts animal welfare and health and the economics and safety of the pork meat supply chain. With emerging information on the gut-brain axis in various animals, scientists are exploring the potential contributions of intestinal microbiota to such behaviors. With recent studies suggesting that there may be a link between observed low diversity in species of Lactobacillaceae and the development of manipulative behaviour, perhaps specific biotics could be used to increase and modulate lactobacilli (selected species and diversity) to control tail and ear biting in pigs. Studies in the future may investigate this possibility.

References

König E, Heponiemi P, Kivinen S et al. Fewer culturable Lactobacillaceae species identified in faecal samples of pigs performing manipulative behaviour. Sci Rep. 2024;14:132. doi: 10.1038/s41598-023-50791-0.

Rabhi N, Thibodeau A, Côté JC, Devillers N, Laplante B, Fravalo P, Larivière-Gauthier G, Thériault WP, Faucitano L, Beauchamp G, Quessy S. Association Between Tail-Biting and Intestinal Microbiota Composition in Pigs. Front Vet Sci. 2020 Dec 9;7:563762. doi: 10.3389/fvets.2020.563762.

Woman holding yogurt. In the US, yogurt now has an approved Qualified Health Claim.

A guide to the new FDA Qualified Health Claim for yogurt

Fermented foods such as yogurt, kimchi, and fermented pickles have traditionally been associated with health benefits in countries around the world, but the science that backs these health benefits is relatively new.

Amidst a growing number of scientific studies examining the health benefits of specific fermented foods, a new Food and Drug Administration (FDA) announcement in the US marks an advance in how the potential benefits of fermented foods can be portrayed to the general public.

In response to a petition by Danone North America, the FDA announced that it will allow the first Qualified Health Claim related to a fermented food – yogurt. The new Qualified Health Claim is worded as follows:

Eating yogurt regularly, at least 2 cups (3 servings) per week, may reduce the risk of type 2 diabetes. FDA has concluded there is limited information supporting this claim.

Or Eating yogurt regularly, at least 2 cups (3 servings) per week, may reduce the risk of type 2 diabetes according to limited scientific evidence.

The claim was announced in a letter of enforcement discretion on March 1st, and can be applied to any yogurt product on the US market that meets the FDA’s standards of identity.

Qualified Health Claims and why they’re important

A Qualified Health Claim is a statement that makes a connection between a substance and a disease-related or health-related condition, is supported by scientific evidence, but does not meet the more rigorous “significant scientific agreement” standard required for an Authorized Health Claim.

Currently, approximately one dozen Authorized Health Claims and around 30 Qualified Health Claims exist in the US for different nutritional and food substances. For example, an Authorized Health Claim exists for soluble fiber from whole oats; Qualified Health Claims exist for walnuts, green tea, and a list of other foods.

To ensure that these claims are not misleading, they must be accompanied by a disclaimer or other qualifying language to accurately communicate to consumers the level of scientific evidence supporting the claim.

According to Bob Hutkins, Professor Emeritus at the University of Nebraska-Lincoln, such claims are important when considered within the context of what Americans currently eat.

He says, “We come nowhere close to eating the recommended amounts of fiber, whole grains, and fruits and vegetables. Indeed, according to the USDA Healthy Eating Index, the average consumer scores a 60 on a 100 point scale. When considering our overall eating habits in the US, I don’t know that this one claim will actually move the needle very much. But in my view, health claims, whether ‘Authorized’ or ‘Qualified’, may help nudge consumers to make informed decisions when deciding what to eat.”

The path to Qualified Health Claim

Dr. Miguel Freitas PhD, VP Health and Scientific Affairs at Danone North America, whose team led the petition, says the company’s efforts were motivated by the observation that, over time, evidence supporting the potential of yogurt to reduce the risk of type 2 diabetes grew more and more compelling.

In December 2018, Danone North America first submitted the Qualified Health Claim petition to the FDA. The petition was put on hold during the height of the COVID-19 pandemic and the evidence was reviewed again in 2023 by the FDA.

In total, more than 85 related studies were considered in support of the claim, with 30 being deemed high or moderate quality.

The FDA gave recognition of the claim in March 2024. Dr. Freitas says, “Now that the claim has been announced, our hope is that it will give consumers simple, actionable information they can use to reduce their risk of developing type 2 diabetes through an easily achievable, realistic dietary modification.”

Scientific support

Prof. Hutkins says the FDA has a high bar even for Qualified Health Claims, requiring a substantial level of scientific evidence to support them. He says that regarding this yogurt claim, “The FDA conducted an exhaustive review of studies that were included in the petition. Many of the studies were not considered rigorous enough and were excluded. In my view, they were very conservative in their analysis of the data.”

Both intervention studies and observational studies were considered in the FDA’s evaluation of the evidence linking yogurt and type 2 diabetes. Pro. Hutkins says that while randomized, controlled trials (RCTs) are considered the gold standard, well-conducted observational studies in large human cohorts can be very informative. The latter ended up being the sole basis of the FDA decision.

“The FDA identified 20 relevant intervention studies, but none were considered sufficiently rigorous to draw meaningful conclusions,” he says. “The FDA identified 28 relevant observational studies, which were then critically reviewed. Ultimately they concluded there was sufficient credible data to suggest associations of yogurt consumption on reduced incidence type 2 diabetes.”

The language for Qualified Health Claims includes any relevant qualifications indicated by the evidence. The FDA claim wording does not differentiate between sweetened and unsweetened yogurt products, with the evaluation noting that the beneficial association was observed irrespective of fat or sugar content. Nevertheless, Prof. Hutkins advises paying attention to the overall nutritional profile of different yogurt products, “In my view consumers could gain the benefits of yogurt without the extra calories and refined carbohydrates by choosing unsweetened yogurts.”

Implications for the food industry

Dr. Freitas says, “Our hope is that this new Qualified Health Claim will inspire the food industry as a whole to increase its focus on yogurt innovation and research, to continue unlocking the full extent of its potential benefits.”

Meanwhile, Prof. Hutkins hopes to see more RCTs on yogurt in the future. “It should be possible to design RCTs that would satisfy the FDA,” he says. “I hope funding agencies will agree.”

Prof. Seppo Salminen PhD, from University of Turku (Finland), says this approval may mark the beginning of a trend in developing claims for individual fermented foods. Such is the goal of a European project called Promoting Innovation of ferMENTed fOods (PIMENTO), which acknowledges the high consumer interest in fermented foods and the potential benefits of these foods for nutrition, sustainability, and more. Prof. Salminen points out that yogurt is leading the way, given the new US claim as well as the existing European Union claim regarding yogurt with live cultures and improved lactose digestion.

Inaugural Sanders Award for Advancing Biotic Science Goes to Argentinian Researcher who leads YOGURITO program

The ISAPP board of directors is pleased to share that the winner of the inaugural Sanders Award for Advancing Biotic Science is Dr. Maria Pía Taranto PhD, a researcher at the Center of Reference for Lactobacilli at the National Scientific and Technical Research Council (CERELA-CONICET) in Argentina.

Dr. Taranto leads the YOGURITO program, established in 2010, which delivers yogurt and other foods enriched with a probiotic to more than 200,000 lower income schoolchildren through a collaboration between scientists, government, industry, and the local community. For this program, Dr. Taranto and colleagues initially assessed candidate strains and selected L. rhamnosus CRL1505, and then led several preclinical and clinical studies demonstrating how it improves immune function. She and her team then developed the partnerships needed to deliver the foods (yogurt, chocolate milk, fresh cheese, and dehydrated powder) free of charge to children in public schools. Dr. Taranto has showed remarkable tenacity and resourcefulness to lead and maintain this program for over a decade in an environment where funding is limited and irregular and where inflation is high. Today the program has a tangible impact on the lives of hundreds of thousands of children per year who may otherwise be at risk of malnutrition.

Dr. Taranto has advanced the biotics field by translating the science and demonstrating real-world impact, using probiotics as a tool to support health in communities with limited resources. In the future she hopes to be able to measure the effects of the probiotic intervention on health and academic outcomes in the children.

After receiving her undergraduate degree in biochemistry and her PhD from National University of Tucuman, Dr. Taranto came to work as a researcher at CERELA-CONICET in 2001. Besides the YOGURITO program, she is involved in research on metabolic and technological aspects of lactic acid bacteria, characterizing new strains for future applications such as in metabolic diseases.

The Sanders Award for Advancing Biotic Science was established in 2023 thanks to the generous contributions of ISAPP community members, to honor the legacy of ISAPP’s former Executive Science Officer, Mary Ellen Sanders PhD. This annual award recognizes someone who has helped advance the biotics field, including probiotics, prebiotics, synbiotics, postbiotics and fermented foods. This year’s committee, composed of ISAPP board members, an industry member representative and Dr. Sanders, selected Dr. Taranto from among the many deserving nominees. Dr. Taranto will receive a cash award and will speak about her work at the ISAPP annual meeting in July, 2024.

2023 in Review: Highlights in the Field of Biotic Science

By Kristina Campbell, Prof. Colin Hill PhD, Prof. Sarah Lebeer PhD, Prof. Maria Marco PhD, Prof. Dan Merenstein MD, Prof. Hania Szajewska MD PhD, Prof. Dan Tancredi PhD, Prof. Kristin Verbeke PhD, Dr. Gabriel Vinderola PhD, Dr. Anisha Wijeyesekera PhD, and Marla Cunningham

Biotic science is an active field, with over 6,600 scientific papers published in the past year. The scientific work that emerged in 2023 covered many diverse areas – from probiotic mechanisms of action to the use of biotics in clinical populations. In parallel with the scientific advancements, consumer interest in gut health and biotics is at an all-time high. A recent survey showed that 67 percent of consumers are familiar with the concept of probiotics and 51 percent of those who consume probiotics do so with the aim of supporting gut health.

Several ISAPP-affiliated experts took the time to reflect on 2023 and identify the most important directions in the fields of probiotics, prebiotics, synbiotics, postbiotics, and fermented foods. Below are these experts’ picks for the top developments in biotic science and application during the past year.

Increased recognition of biotics as a category

After ISAPP’s publication of the recent synbiotics and postbiotics definitions in 2020-2021, board members and others began referring to probiotics, prebiotics, synbiotics, and postbiotics collectively as “biotics”. 2023 has seen the term being used more widely (for example, in article headlines and communications from major organizations) to refer to these substances as a broad group.

Steps forward and steps back in the regulation of live microbial interventions

The actions of regulators have a profound impact on how biotic science is applied and how products can reach consumers. On the positive side, 2023 heralded the regulatory approval of two live microbial drug products for recurrent C. difficile infection by the US Food and Drug Administration (FDA). Both products are derived from fecal samples, but one is delivered to the patient gastrointestinal (GI) tract by enema, and the other is delivered orally.

Meanwhile, a case of fatal bacteremia in a preterm infant who had been given a probiotic product prompted the FDA to issue a warning letter to healthcare practitioners about probiotics in preterm infants, as well as warning letters to two probiotic manufacturers. These actions had the concerning effect of reducing access to probiotics for this population, despite the accumulated evidence that probiotics effectively prevent necrotizing enterocolitis in preterm infants. As outlined in ISAPP’s scientific statement on the FDA’s actions, the regulatory decision weighting the risks of commission over omission did not reflect the wealth of evidence for probiotic efficacy in this population and the low risk of harm.

Wider awareness of the postbiotic concept and definition

Scientific discussions on postbiotics continued throughout 2023, with several debates and conference sessions devoted to discussion of the postbiotic concept – including the status of metabolites in the definition. According to ISAPP board member Dr. Gabriel Vinderola PhD, who was a co-author on the definition paper and an active participant in many of these debates, the ISAPP definition is gaining traction and the debates have been useful in pinpointing further areas of clarification for the sake of regulators and other stakeholders. As shared with the audience at Probiota Americas 2023 in Chicago, Health Canada became the first regulatory agency to address the definition, and has started considering the term postbiotics under the ISAPP definition.

Advances in technologies for analyzing different sites in the digestive tract

When studying how biotics interface with the host via the gut microbiota, the science has relied mainly on analysis of fecal samples, with the majority of the GI tract remaining a ‘black box’. But a 2023 paper by Shalon et al., which was discussed at the ISAPP meeting in Denver, describes a device able to collect intestinal samples from different regions in the GI tract. Analysis of the metabolites and microbes indicated clear regional differences, as well as marked differences between samples in the GI tract versus fecal samples (for example, with respect to bile acids); an accompanying paper revealed novel insights into diet and microbially-derived metabolites. Efforts are underway across the world to develop smart pills or robotic pills that take samples all along the GI tract. Some devices have sensors that immediately signal to a receiver and others have been engineered to release therapeutic contents. Although these technologies may need more validation before they are useful in research or clinical contexts, they may greatly expand knowledge of the intestinal microbial community and how it interacts with biotic substances.

First convincing evidence linking intake of live microbes with health benefits

When an ISAPP discussion group in 2019 delved into the question of whether a higher intake of safe, uncharacterized live microbes had the potential to confer health benefits, it spurred a program of scientific work to follow. Efforts of this group in subsequent years led to the publication of an important study in 2023: Positive Health Outcomes Associated with Live Microbe Intake from Foods, Including Fermented Foods, Assessed using the NHANES Database. Researchers analyzed data from a large US dietary database and found clear but modest health benefits associated with consuming higher levels of microbes in the daily diet.

The benefits of live dietary microbes are being explored further in the scientific literature (for example, here, here, and here) and are likely to remain an exciting topic of study in the years ahead, building evidence globally for the health benefits of consuming a higher quantity of live microbes.

Increased interest in candidate prebiotics

Polyphenols have long been studied for their health benefits, but newer evidence suggests they may have prebiotic effects, achieving their health benefits (in part) through interactions with the gut microbiota. A theme at conferences and in the scientific literature has been the use of polyphenols to modulate the gut microbiota for specific health benefits. More than a dozen reviews on this topic were published in 2023, and several of them focused on how polyphenols may achieve health benefits in very specific conditions, such as diabetes or inflammatory bowel disease.

Another substrate receiving much attention for its prebiotic potential are human milk oligosaccharides (HMOs). HMOs, found in human milk, support a nursing infant’s health by encouraging the growth of beneficial gut microbes. Several articles in 2023 have delved into the mechanisms of HMO metabolism by the gut microbiota, and explored its potential as a dietary intervention strategy to improve gut health in adults.

Sharper focus on evidence for the health and sustainability benefits of fermented foods

Fermented foods are popular among consumers, despite only early scientific knowledge on whether and how they might confer health benefits (see ‘First convincing evidence linking intake of live microbes with health benefits’, above). ISAPP board member Prof. Maria Marco PhD co-authored a review led by Dr. Paul Cotter PhD in Nature Reviews Gastroenterology and Hepatology on the GI-related health benefits of fermented foods. The paper clearly lays out the potential mechanisms under investigation and identifies gaps to be addressed in the ongoing study of fermented foods.

As calls for reducing carbon footprints continue across the globe, plant-based fermented foods are being singled out as an area for innovation and expansion. One example of how these foods are being explored is through the HealthFerm project, a 4-year, 13.1 million Euro project involving 23 partners from 10 countries, which is focused on understanding how to achieve more sustainable, healthy diets by leveraging fermented foods and technologies.

Novel findings related to lactic acid bacteria

Lactic acid bacteria (LAB) are some of the most frequently-studied microbial groups, but scientists have only begun to uncover the workings of this diverse group of bacteria and how they affect a variety of hosts. These bacteria are used as probiotics and are often beneficial members of human and animal microbiomes, and they are also essential to making fermented foods. This year marked the first ever Gordon Research Conference on LAB in California, USA. Attendees showcased the diversity of research on lactic acid bacteria, and the meeting was energized by the early investigators present and by the interest in LAB in other disciplines including medicine, ecology, synthetic biology, and engineering. One example of a scientific development in this area was the further elucidation of the mechanism of Lactiplantibacillus plantarum’s extracellular electron transfer.

Progress on the benefits and mechanisms of action for probiotics to improve the effectiveness of cancer immunotherapies

Researchers have known for several years that the gut microbiota can be a determinant of the efficacy of cancer immunotherapy drugs that involve immune checkpoint blockade, but interventions that target the gut microbiota to improve response to immunotherapies have been slower to develop. This year saw encouraging progress in this important area, with probiotic benefits and mechanisms of action being demonstrated in several papers. Two of the most highly cited probiotics papers of the year centered on this topic: one showing how a tryptophan metabolite released by Limosilactobacillus reuteri (formerly Lactobacillus reuteri — see this ISAPP infographic) improves immune checkpoint inhibitor efficacy, and another paper that reviewed how gut microbiota regulates immunity in general, and immune therapies in particular.

Updated resource available on probiotics and prebiotics in gastroenterology

This year the World Gastroenterology Organisation (WGO) guidelines on probiotics and prebiotics were updated to reflect the latest evidence, with contributions from ISAPP board member Prof. Hania Szajewska MD PhD and former board member Prof. Francisco Guarner MD PhD. The guideline lists indications for probiotic and prebiotic use, and how the use of these substances may differ in pediatric versus adult populations. Find the guideline here.

Statistical considerations for the design of randomized, controlled trials for probiotics and prebiotics

By Prof. Daniel Tancredi, UC Davis, USA

The best evidence for the efficacy of probiotics or prebiotics generally comes from randomized controlled trials. The proper design of such trials should strive to use the available resources to achieve the most informative results for stakeholders, while properly accounting for the consequences of correct and incorrect decisions. It is crucial to understand that even well-designed and -executed studies cannot entirely eliminate uncertainty from statistical inferences. Those inferences could be incorrect, even though they were made rigorously and without any procedural or technical errors. By “incorrect”, I mean that the decisions made may not correspond to the truth about those unknown population parameters. Those parameters involve the distribution of study variables in the entire population, but our inferences are inductive and based on just the fraction of the population that appeared in our sample, creating the possibility for discordance between those parameters and our inferences about them. Although rigorous statistical inference procedures can allow us to control the probabilities of certain kinds of incorrect decisions, they cannot eliminate them.

For example, consider a two-armed randomized controlled trial designed to address a typical null hypothesis, that the probability of successful treatment is the same for the experimental treatment as for the comparator. Depending on the analytical methods to be employed, that null hypothesis could also be phrased as saying that the difference in successful treatment probabilities between the two arms is zero or that the ratio of the successful treatment probabilities between the two groups is one. Suppose the study sponsor has two possible choices regarding the null hypothesis, either to reject it or fail to reject it. (The latter choice is colloquially called “accepting the null hypothesis”, but that is a bit of an overstatement, as the absence of evidence for an effect in a sample typically does not rise to the level of being convincing evidence for the absence of an effect in the population.)

With these two choices about the null hypothesis, there are two major types of “incorrect decisions” that can be made: the null hypothesis could be true for the population but the study data led to a decision to reject the null hypothesis, a result conventionally called a “Type-1” error. Or the null hypothesis could be false for the population but the study data led to a decision not to reject the null hypothesis, conventionally called a “Type-2” error. Conversely, there are also two potentially correct decisions. One could fail to reject the null hypothesis when the null hypothesis is true for the population, a so-called “true negative”, or one could reject the null hypothesis when the null hypothesis is not true, a so-called true positive.

The consequences of these four different decision classifications vary from one stakeholder to another, and thus it is unwise to rely solely and simply on commonly used error probabilities when planning studies. The wiser approach is to set the error probabilities so that they properly account for the relative gains and losses to a stakeholder that arise from correct and incorrect decisions, respectively. From long experience assessing the design of clinical trials for probiotics and prebiotics, I recommend that stakeholders in the design phase of studies give thought to the following three statistical considerations.

Pay attention to power

Power is the probability of avoiding a type-2 error—in other words, under the condition that an assumed true effect exists in a study population and that the type-1 error has been controlled at a given value, power is computed of the probability of avoiding the incorrect decision to fail to reject the null hypothesis. Standard practices are to set the type-1 error at 5% and to determine a sample size that achieves 80% power for an assumed alternative hypothesis, one stating that the true effect is of a specific given magnitude, one corresponding to a so-called meaningful effect size. That effect size is typically called a ‘minimum clinically significant difference’ (MCSD) or something similar, because ideally the assumed effect size would be the smallest of the values that would be clinically important, although as a practical matter — because the higher the magnitude of the effect size, the lower the sample size requirements and thus the better the chance of the study being perceived as “affordable” to study sponsors — the MCSDs used to power studies are often larger than some of the values that would also be clinically significant. Nevertheless, let’s consider what it means for the sponsor to accept that the study should be powered at merely the conventional 80% level. Under the assumptions that the true effect in the population is the MCSD and that the study achieves its target sample size, a sponsor of a study that has only 80% power is taking a 1-in-5 chance that the sample results would not be statistically significant (and that the null hypothesis would fail to be rejected).  Such an incorrect decision could have major adverse implications for the sponsor (and for potential beneficiaries of the intervention), particularly given the investments that have been made in the research program and the implications the incorrect decision could have for misinforming future decisions regarding the specific intervention and indeed related interventions.  A 20% risk may not be worth taking.

All other considerations being equal, the risk of a type-2 error could be lowered by increasing the sample size. Under regular asymptotic assumptions that generally apply, increasing the target sample size by about one-third would cut a 20% type-2 error risk in half, to 10%. Increasing the target sample size by two-thirds reduces it all the way to 5%.

Define the true minimum clinically significant effect size applicable to your study

Another important question is where to set the minimum clinically significant effect. Often that effect is based on prior studies without any adjustment—but this can neglect key considerations. Prior effects of an intervention are typically biased in a direction that overstates the benefits of the intervention, especially if the intervention emerged from smallish early-phase studies. More fundamentally, from the perspective of decision theory the estimated effects seen in prior studies do not specifically address what could truly be the minimum clinically meaningful effect when one considers the possible benefits, risks, and costs of the intervention. Probiotics and prebiotics are typically relatively benign interventions in terms of adverse events, so it could be that even more modest favorable impacts on health than were seen in prior studies are still worthwhile.

Powering your study based on what truly is a minimal clinically meaningful effect may lead to a better overall strategy for optimizing net gains, while giving the intervention an appropriately high chance of showing that it works. Although the smaller the assumed effect size, the larger the required sample size needed to detect it (all other factors being the same), a proper assessment of the relative risks and benefits of the intervention and, also, of correct and incorrect decisions about the intervention, may provide a strong basis for making that investment.

In addition, there is another important but often overlooked aspect when deciding on what is a worthwhile improvement. We frequently turn to clinicians to determine what would be a worthwhile improvement, and it is natural for a clinician to address that question by considering what would be a meaningful improvement for a patient who responds to the intervention. Keep in mind, though, that an intervention could be worthwhile for a population if it achieves what would be a worthwhile improvement for a single patient–say, a mean improvement of 0.2 SD on a quality-of-life scale—in only a fraction of the patients in the overall population, say 50%. There are many conditions for which having an intervention that works for only large subsets of the population could be valuable in improving the population’s overall health and wellness. Using this example, where the worthwhile improvement for an individual is 0.2 SD and the worthwhile responder percentage is 50%, then the worthwhile improvement that should be used to power the study would be 0.1 SD, which is equal to (0.2 SD * 50%) + (0 SD * 50%), with the latter product quantifying an assumed absence of a benefit in the non-responders. What should be gleaned from this example is that the minimum clinically important effect for a population is typically less than the minimum clinically important effect for an individual. The effect used to power the study should be the one that applies to the relevant population. Again, that effect should be chosen so that it balances benefits relative to the costs and harms of the intervention while accounting also for variation in whether and how much individuals in the population may respond. When study planners fail to account for this variation, the result is a study that is underpowered for detecting meaningful population-level effects.

Improving the signal-to-noise ratio

In general, effect sizes can be expressed analogously to a mean difference divided by a standard error, and thus can be thought of as a signal-to-noise ratio. Sample size requirements depend crucially on this signal-to-noise ratio. Typically, standard errors are proportional to outcome standard deviations and inversely proportional to the square root of the sample size. The latter is key because it means that in case an expected signal would be cut in half, the noise would also need to be cut in half to maintain the signal-to-noise ratio, which means that if you cannot alter the outcome standard deviation, then you would need to quadruple the sample size. This also applies in the opposite direction, happily: if you can double the expected signal-to-noise ratio, you would only need one-fourth the sample size to achieve the desired power, all other things being equal.

Signal-to-noise ratios can be optimized by designing a trial for a judiciously restricted target population (of potential responders) and by using high-quality outcome measurements for the trial to reduce noise. Although research programs may eventually aim to culminate in large pragmatic trials that show meaningful improvements associated with an intervention even in populations of individuals with wide variations in their likelihood and amount of potential response, it is generally wise up to that stage in a research program to focus trials so that they give accurate information as to whether the intervention works in populations targeted for being more apt to be responsive to an intervention. To do that, for example, the trial methods should include accurate assessments for whether potential recruits are currently experiencing, say, symptoms from whatever condition the intervention is intended to address and whether the recruit would be able to achieve the desired dose of whatever the trial assigns to them. For a truly beneficial intervention, it is easier to continue a research program advancing the development of that intervention if the intervention sustains a consecutive string of “true positive” results from when it began to undergo trials, avoiding a potentially fatal type-2 error (“false negative”).

Careful attention to the above considerations can lead to better trials, ones that combine rigor and transparency with a tailored consideration of the relative costs and benefits of potentially fallible statistical inferences, so that the resulting evidence is as informative as possible for stakeholder decision-making.

New paper outlines the value of studying probiotics in the small intestine

Even though the human digestive tract extends from the mouth down through the small and large intestines, the study of probiotics and their activities has tended to focus on the colon. While the colon (or perhaps more accurately its proxy, the faecal sample) is relatively accessible and easy to study, recently some researchers have argued that crucial information can be gained from looking at another digestive tract site: the small intestine.

A recent paper published in Cell Reports Medicine, titled Small intestine vs. colon ecology and physiology: Why it matters in probiotic administration, laid out the differences between probiotic actions and interactions in the small intestine versus the large intestine. The paper was the result of work by an expert group of the International Life Sciences Institute (ILSI) Europe – the Probiotics Taskforce.

The authors of the paper say the duodenum (the first part of the small intestine) is the most dynamic part of the digestive tract. The small intestine as a whole is the site where most of the body’s digestion and absorption takes place, it is also a site of high immune activity. Even though ingested materials move through this area more rapidly than the large intestine, the small intestine allows closer interaction between host and microbes because it has a lower rate of mucus secretion and looser gut barrier junctions. The microbiota of the small intestine is primarily shaped by the digestion and resulting abundance of simple carbohydrates and amino acids, whereas the colonic microbiota is driven by the metabolism of the remaining complex carbohydrates. These factors and others create very different environments for probiotic interaction and activity.

While the most relevant clinical question for a probiotic strain may be what health benefit it confers in the host, researchers may also be interested in gut microbiota manipulation via probiotics to transform host-microbe interactions at discrete locations in the digestive tract – potentially yielding new or improved benefits for the host. The paper raises the possibility of novel probiotics discovered or developed in the future to specifically target the small intestine.

Accessibility of the small intestine, however, remains a challenge. While animal and in vitro models can lead to valuable insights, the authors of the paper point to the need for more sensitive and cost-effective tools for sampling the small intestine in human study participants.

See this Q&A with the paper’s lead author, Dr. Arthur Ouwehand PhD, Global Health & Nutrition Sciences, International Flavors & Fragrances, Finland.

Why is it important to think about how probiotics interact at sites other than the colon?

Nutrient absorption, entero-hepatic circulation, and energy regulation are all happening in the small intestine and have a major impact on our health. Even some forms of diarrhoea originate from the small intestine. So, we should be better aware what happens in the small intestine and how probiotics may influence these processes.

What clues do we have that the small intestine is an important site for probiotic activity?

The most common argument is that the microbial numbers in the small intestine are much smaller and hence (with less competition) probiotics can better exert an effect there. Is that true? We don’t know yet, because small intestinal samples have been difficult to collect. We need to better understand what is happening in the human small intestine.

Do small intestinal interactions depend on the specific probiotic?

Very likely. Also interesting is how diet would shape the effects of the probiotic in the various parts of the small intestine.

What are some of the main questions researchers still need to address regarding how probiotics act in the small intestine?

  • What is the microbiota in the small intestine and how is it influenced?
  • What do these changes in composition and activity mean?
  • How can the small intestinal microbiota be influenced in a meaningful way?

How do you think researchers will overcome the challenges of gathering information about the small intestine?

Capsules that sample the small intestine are nothing new. They were already developed in the 1960s. Better and more affordable capsules are now coming on the market, so minimally invasive sampling of the human small intestine will soon be much more feasible. These new technologies should expand our understanding of the microbiota in different parts of the small intestine, and how probiotics interact in this environment.

Bridging the Gap Between Probiotic and Microbiome Research

By Prof. Sarah Lebeer PhD, University of Antwerp, Belgium

September was an eventful month for me, as I had the privilege of participating in various scientific gatherings. These include co-organizing the 14th Symposium on Lactic Acid Bacteria (LAB14) in the Netherlands (LAB symposium), attending the European Helicobacter and Microbiota Study Group workshop (EHMSG) in my hometown of Antwerp, joining the Human Microbiome Symposium at EMBL Germany, and participating in the 7th International Conference on Microbial Diversity conference in Parma. These events provided me with valuable opportunities to share insights from our Isala vaginal microbiota project (https://isala.be/en) and to engage with leading scientists in the fields of the human microbiome, fermented foods, and probiotics, such as Martin Blaser, Maria Gloria Dominguez-Bello, Curtis Huttenhower, Jeroen Raes, Peer Bork, Rob Knight, Gene Tyson and Paul Cotter, just to name a few.

Reflecting on these recent interactions, I find it intriguing that the term ‘probiotics’ is relatively infrequently used in discussions at typical microbiome conferences or sessions. It has struck me that a descriptive microbiome study in a specific cohort or patient group often garners more scientific recognition than a human intervention study involving probiotics, which target the microbiome to induce a particular change in health parameters. It’s worth noting that many large-scale solid microbiome papers are published in high-impact journals, whereas probiotic studies tend to find their home in journals with lower impact factors. This discrepancy exists even when most associations observed in microbiome studies are primarily descriptive rather than causal. I must admit to this bias in our own work, having recently published a substantial cohort study (the Isala study) on the vaginal microbiome with over 3300 participants in Nature Microbiology, while our probiotic studies typically appear in lower-impact journals (e.g. this study). Although our Isala study yielded valuable insights, it could only associate 10.4% of questionnaire responses with features of the microbiome composition, with associations rather than causal relationships identified. Nevertheless, we plan to explore these findings further through intervention studies (including probiotic, dietary, and lifestyle interventions) and more mechanistic research (https://isala.be/en ). Similarly, the extensive gut microbiome cohort study conducted by Jeroen Raes’ team in Belgium and published in Science could explain only 7.6% of the associations with the extensive metadata collected.

While we do all acknowledge the value and strength of such large microbiome cohort studies, probiotic intervention studies offer a unique advantage in investigating causality. In such studies, live microorganisms (or mixtures thereof) are deliberately administered in specific formulations and evaluated for their health benefits to the host. Probiotics often do not work via (gut) microbiome modulation (as more broadly discussed in this ISAPP podcast episode), but undoubtedly interact in the same complex environment. ISAPP has long championed the importance of rigorous and well-controlled clinical trials to assess the value of interventions, but the results, while scientifically valuable, are seldom sensational. This shouldn’t come as a surprise because modifying the health status of a living host with a single intervention, be it a probiotic or a single drug molecule, is a complex task. If you’ve ever listened to a lecture or read a paper by ISAPP President Dan Merenstein (if not, check this ISAPP podcast episode), you’ll recall his emphasis on the high number-needed-to-treat (NNT) in many traditional drug interventions. If these NNTs are compared for some drugs with probiotics, probiotics actually do not perform badly, and often outperform other interventions in terms of safety.

Probiotics, by their nature, have a multifaceted mode of action, attributed to their status as live microorganisms with an average of 3000 genes and probably even more bioactive molecules expressed. Their effects in a living host are diverse and context-dependent, involving complex modulation of biochemical, immune, and other pathways. While I haven’t conducted the statistical calculations myself, the likelihood of detecting a significant and large-scale effect in probiotic intervention studies does not appear high, especially given that the average probiotic intervention study involves around 74 participants, rarely exceeding 200 participants .

This limitation has contributed to an underwhelming reputation for the science behind probiotics despite the many health benefits demonstrated, as these trials are typically small in scale and constrained by limited budgets and limited number of parameters under investigation. Most of these studies are carried out by university and food company researchers with budgets significantly smaller than those in the pharmaceutical industry, where studies can cost around $40,000 per participant. The microbiome therapeutics and live biotherapeutics (LBPs) field, which includes probiotic products for therapeutic indications and routes, is gradually moving towards more expensive pharmaceutical-style trials, with some FDA-approved trials featuring GMP-produced LBPs. Success stories like REBYOTATM (from Ferring and Rebiotix) and VOWST (formerly SER-109, from Seres) have demonstrated significant benefits in specific conditions (C. difficile infection), which have reduced heterogeneity from the host side. Yet, participant numbers in these trials remain in the same range as many probiotic intervention studies.

Given the available funding from both private and public sources, organizing large clinical trials with specifically designed probiotics as LBPs for all promising health conditions under stringent pharmaceutical conditions is an unrealistic prospect. If probiotic strains can be delivered orally as food supplements, it is likely that current trial practices will continue to be preferred due to budget, logistical, and regulatory considerations, even though they may have limitations in claiming health benefits under less rigorous conditions. These studies, if conducted and analyzed diligently, can still yield valuable and meaningful results.

As scientists actively engaged in both the microbiome and probiotic fields, we should seek greater unity. We must recognize that the science of how live microbes interact with a living host is inherently complex and rarely boils down to a single mode of action resulting in spectacular effects. Although the intended use of probiotics and LBPs differs, both share similar scientific challenges. ISAPP’s definition of probiotics is a valid attempt to embrace this complexity and can apply to most microbial therapeutics or LBPs if the administered microorganisms are well-characterized and quality-controlled.

Let’s acknowledge that, despite their challenges, probiotic trials have already contributed and will likely continue to contribute) unique insights into the intricate world of host-microbe interactions, and these insights can be harnessed to improve human health.

Why responders and non-responders may not be the holy grail for biotics

By Prof. Dan Merenstein MD, Georgetown University Medical Center, USA

In September the New York Times published an article titled “What Obesity Drugs and Antidepressants Have in Common. It was written by a physician who had personally struggled with weight issues and depression. In his personal journey with these health challenges, he hesitates to undergo any treatments. But he eventually does and experiences much relief from them. Why would a practicing physician hesitate to use approved drugs?

The article opens with this viewpoint: “We like to think we understand the drugs we take, especially after rigorous trials have proved their efficacy and safety. But sometimes, we know only that medications work; we just don’t know why.” He goes on to discuss selective serotonin reuptake inhibitors (SSRIs) and  the recently approved weight loss drugs, such as glucagon-like peptide-1 (GLP-1) receptor agonists. The former have been widely used for over 40 years, while the weight loss drugs are more recent. For both classes of drugs, we have some ideas how they work but the exact mechanisms have not been elucidated. While this knowledge gap has not prevented wide usage, the author of the article was skeptical about using the drugs if he did not know exactly how they worked. 

When I started studying probiotics 15 years ago, I began to interact with a different group of scientists than I was used to. My new collaborators were basic and applied scientists, not just clinicians. I had opportunities to attend conferences that covered bench science more than clinical evidence.  My perspective as a clinical researcher was different from most of the others in attendance. I was somewhat surprised to learn how much emphasis those scientists placed on understanding mechanisms. On the one hand, intuitively it makes sense. If you know how something functions, you have a lot more confidence that it will do what you expect it to do, and more assured that it can be used safely. You also have a sense that it should work for you. But on the other hand, knowing an intervention is effective is more important than knowing how it achieves its effectiveness.

This emphasis on understanding mechanisms of action for interventions reminds me of the development of beta-blockers, a class of medicines that block epinephrine, and cause the heart to beat slower and with less force. One of the most common test questions I was asked when I was a medical student and resident is: What class of blood pressure medicines are never permissible for a patient with congestive heart failure (CHF)? Well it was obvious to all of us that the answer was clearly beta-blockers, as you wouldn’t want to slow the heart rate and reduce the force of the heart in a patient already suffering from a poorly performing heart. Yet after clinical trials were completed, beta-blockers were shown to be effective treatment for CHF patients and are now a mainstay of CHF treatment. This was counterintuitive considering the drug’s mechanism of action. So in fact, a drug’s mechanism of action does not always lead in a straightforward way to knowledge about which conditions can be treated or which individuals will respond.

Beyond mechanisms of action and individual response

In clinical medicine, we use two important statistics to capture efficacy and safety of an intervention: number needed to treat (NNT) and number needed to harm (NNH). NNT is the number of patients that need to be treated in order to have an impact on one person, while the NNH is the number of patients who must be treated with an intervention before one patient is harmed.  All interventions have both an NNT and NNH. Obviously, the goal is  a very low NNT and a high NNH. But we are rarely so fortunate. Take for example statins, a medicine many of us take. In patients at low risk of cardiovascular disease, the NNT is 217, which means 1 person out of 217 avoided a nonfatal heart attack by taking statins. Meanwhile, NNH for muscle pain is 21 and for developing diabetes is 204.

NNT and NNH are rarely considered in the biotics field. Yet I commonly encounter discussions about the importance of identifying responders versus non responders to biotic intervention and the need to elucidate the mechanism(s) of action for biotic substances. I believe this is because many of the scientists doing research in biotics come not from a clinical background but more bench research, where the questions really are those of mechanism. Many seem to believe that such knowledge is the Holy Grail of biotics – if only scientists could have such a good grasp of mechanism that they could figure out why certain people responded while others do not. There is nothing inherently wrong with wanting to identify reasons for differences in individual response. It is what we do in clinical practice every day. When I give someone blood pressure medicine and they don’t respond to it, I wonder – Is it a compliance issue? Is the patient’s blood pressure caused by something that the medicine does not impact? Is the patient taking the medication at the wrong time, with the wrong diet, or with other interfering medicines?  Clinicians always must think about who is responding and who is not responding. However, NNT and NNH for biotics are worth prioritizing.

Data have shown that certain probiotics can get people better from an upper respiratory tract infection 26 hours earlier, or can treat infantile colic, or improve irritable bowel syndrome symptoms with a NNT respectively of 20, 15 and 100, while having a very high NNH. These are great products. But instead what I often hear at conferences is that we need to figure out why some people respond to the probiotics and others do not. I agree, go ahead and figure it out. But have realistic expectations. If two of the most widely used medicines, SSRIs and GLP-1 agonists, have an unclear mechanism, and if statins have an NNT of 217, be realistic about the impact of your probiotic. When a doc prescribes you Lipitor, he doesn’t say, “Good luck –  I hope you are the 0.4% in which it helps and aren’t the 5% that gets muscle cramps.” The hope is that for you, the NNT is 1. And when your strain or product does have an impact, feel free to find ways to improve efficacy but celebrate the impact it has. If possible, maybe compare your NNTs to standard of care, or if no comparison look at your NNT versus NNH to really better understand what your biotic can do.

Probiotic Administration in Preterm Infants: Scientific Statement

Board of Directors, International Scientific Association for Probiotics and Prebiotics

in collaboration with

Dr. Geoffrey Preidis MD PhD, Pediatric Gastroenterology, Hepatology & Nutrition

Prof. Andi L Shane MD MPH MSc, Pediatric Infectious Diseases

A recent report of a fatality in an extremely premature infant recipient of a probiotic product has resulted in a warning letter from the United States Food & Drug Administration (FDA) to healthcare practitioners about probiotic supplementation in preterm infants and a warning letter to the probiotic product manufacturer.

Publicly available information suggests that this fatality was the direct consequence of bacteremia resulting from ingestion of the probiotic organism Bifidobacterium longum subsp. infantis delivered in medium chain triglyceride oil. This situation differs from case reports of adverse events that resulted from extrinsic probiotic product contamination (1, 2). This is an important distinction, as the potential risks and mitigation strategies differ between etiologies. As complete details of this most recent fatality have not been released, specific factors that may have contributed to the adverse outcome are unknown. However, it is worth considering the context of this case report within the broader literature available on probiotic use in this population, including the wealth of data available on sepsis incidence.

Evidence from systematic reviews

Premature infants, especially those of <32 weeks gestation and with a birth weight <1500 g, are a vulnerable population at significant risk of morbidity and mortality.  Necrotizing enterocolitis (NEC) is highly prevalent (5-10% incidence) among very preterm infants, with mortality rates of 20-30% and high morbidity among survivors, including short gut syndrome, parenteral nutrition-associated liver disease, and neurocognitive delay.

A large body of literature exists on the use of probiotics in hospitalized preterm infants, with particular focus on the prevention of NEC. At least 85 randomised clinical trials (RCTs) (3) have been conducted to evaluate the use of probiotics in preterm infants for the prevention of diseases associated with prematurity, and a number of systematic reviews with meta-analyses have analysed these data in recent years. Most RCTs conducted in the neonatal intensive care unit (NICU) designate sepsis as one of the main outcome measures.

The most recent meta-analysis was published online October 2 in JAMA Pediatrics (3). This study included 106 trials on probiotic, prebiotic, synbiotic and lactoferrin interventions for either preterm infants <37 weeks and/or those with low birth weight (<2500 g). Administration of probiotics containing multiple strains were found to be most effective in the reduction of all-cause mortality (31% reduction), with a 62% decrease in incidence of severe NEC compared to placebo (moderate and high certainty evidence). Single strain probiotics combined with lactoferrin provided greatest efficacy in the reduction of late-onset sepsis incidence (67% risk reduction with moderate certainty evidence). It was noted that none of the included studies reported cases of probiotic-induced sepsis.

Other authors including groups from the Cochrane Collaboration, American Gastroenterological Association (AGA) and the European Society for Paediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) have found similar results, and studies can be reviewed here:

Probiotics to prevent necrotising enterocolitis in very preterm or very low birth weight infants – Sharif, S – 2023 | Cochrane Library

Probiotics Reduce Mortality and Morbidity in Preterm, Low-Birth-Weight Infants: A Systematic Review and Network Meta-analysis of Randomized Trials – Gastroenterology (gastrojournal.org)

Probiotics for Preterm Infants: A Strain-Specific Systematic… : Journal of Pediatric Gastroenterology and Nutrition (lww.com)

No meta-analysis has attributed increased risk of sepsis to probiotic use in preterm infants – rather, in many cases a protective effect (or a trend toward protection) was reported. However, it is important to acknowledge the real but rare risk of probiotic-induced bacteremia in this population. In a recent review of case reports of probiotic-associated invasive infections in children, probiotic-induced bacteremia in premature infants were found to have resolved in most cases with use of effective antimicrobial therapy (4).

With data collected on over 10,000 preterm infants, substantial benefits demonstrated and a low level of risk identified, promise to improve outcomes in preterm infants who receive a probiotic product currently exists. Based on the evidence currently available, hospitals and NICUs across the globe have already adopted practices relating to probiotic use in preterm infants, some with significant health impacts (5, 6).

Risk benefit analysis and considerations for healthcare implementation

Further work needs to be done to support probiotic administration in the NICU. Collaborative efforts include recommendations for practical steps to improve probiotic product quality assurance specifically for NICU use, published in July 2023 in JAMA Pediatrics (7).

It is important to note that few (or possibly no) effective interventions are without an adverse event profile, and probiotics are no exception. Even food has a safety standard of reasonable certainty and on a regular basis, individuals suffer fatal foodborne infections. When considering the clinical indications for any intervention for an individual patient or a population of individuals, a thorough comparison of all available data on both the potential risks and the potential benefits is warranted.

The American Gastroenterological Association (8) and other major societies (including ESPGHAN and the World Gastroenterology Organisation) (9, 10) endorse probiotic products for the prevention of NEC among preterm low birth weight infants. The societies’ guidelines agree that the recommendation to use probiotics is conditional. Conditional recommendations are sensitive to patients’ values and preferences, and to the guideline panel’s perception of risk-benefit balance.  However, the recent FDA letter does not acknowledge these recommendations and further, recommends against probiotic use in preterm infants despite the robust efficacy data. With interventions such as probiotic administration, ideally shared clinical decision-making with patient and clinician would ensue. Regulatory warnings inform the risk-benefit calculation but typically do not invalidate a clinical recommendation.

Summary

  • Probiotic administration to preterm infants has been demonstrated to significantly reduce the risk of NEC, sepsis and death in large systematic reviews with meta-analyses.
  • Meta-analyses have not identified significant adverse events or safety concerns, although rare case reports have documented sepsis attributed to probiotics.
  • Stringent manufacturing standards are recommended for probiotics in vulnerable populations such as preterm infants.
  • Standardized comprehensive safety reporting across probiotic intervention studies is needed, along with funding for the conduct of long term studies.
  • The risks and benefits of probiotic administration should be considered in both the specific population and individual patients, with regulatory frameworks to enable implementation.
  • More information about this fatality should be immediately released so healthcare professionals and researchers can learn from this experience and continue to provide optimal evidence-based patient care.

To inquire about expert academic physicians available for media comment, please contact ISAPP’s Executive Director, Marla Cunningham, at marla@nullisappscience.org

See also:

NEC Society: Statement on FDA Warning of Probiotics in Preterm Infants

References

(1) Vallabhaneni S, Walker TA, Lockhart SR, et al. Notes from the field: Fatal gastrointestinal mucormycosis in a premature infant associated with a contaminated dietary supplement–Connecticut, 2014. MMWR Morb Mortal Wkly Rep. 2015;64(6):155-156.

(2) Bizzarro MJ, Peaper DR, Morotti RA, Paci G, Rychalsky M, Boyce JM. Gastrointestinal Zygomycosis in a Preterm Neonate Associated With Contaminated Probiotics. Pediatr Infect Dis J. 2021;40(4):365-367.

(3) Wang Y, Florez ID, Morgan RL, et al. Probiotics, Prebiotics, Lactoferrin, and Combination Products for Prevention of Mortality and Morbidity in Preterm Infants: A Systematic Review and Network Meta-Analysis. JAMA Pediatr. 2023 Oct 2:e233849.

(4) D’Agostin M, Squillaci D, Lazzerini M, et al. Invasive Infections Associated with the Use of Probiotics in Children: A Systematic Review. Children (Basel). 2021 Oct 16;8(10):924.

(5)  Rath CP, Athalye-Jape G, Nathan E, et al. Benefits of routine probiotic supplementation in preterm infants. Acta Paediatr. 2023 Jul 28.

(6) Bui A, Johnson E, Epshteyn M, Schumann C, Schwendeman C. Utilization of a High Potency Probiotic Product for Prevention of Necrotizing Enterocolitis in Preterm Infants at a Level IV NICU. The Journal of Pediatric Pharmacology and Therapeutics 2023;28(5):473–475.

(7)  Shane AL, Preidis GA. Probiotics in the Neonatal Intensive Care Unit-A Framework for Optimizing Product Standards. JAMA Pediatr. 2023 Sep 1;177(9):879-880.

(8) Su GL, Ko CW, Bercik P, et al. AGA Clinical Practice Guidelines on the Role of Probiotics in the Management of Gastrointestinal Disorders. Gastroenterology. 2020 Aug;159(2):697-705.

(9) WGO Practice Guideline: Probiotics and Prebiotics. Available from: https://www.worldgastroenterology.org/guidelines/probiotics-and-prebiotics

(10) van den Akker CHP, van Goudoever JB, Shamir R, et al. Probiotics and Preterm Infants: A Position Paper by the European Society for Paediatric Gastroenterology Hepatology and Nutrition Committee on Nutrition and the European Society for Paediatric Gastroenterology Hepatology and Nutrition Working Group for Probiotics and Prebiotics. J Pediatr Gastroenterol Nutr. 2020 May;70(5):664-680.

Gut microbiota from a surprising source—baby kangaroos—might decrease cattle methane production

By Prof. Seppo Salminen, University of Turku, Finland

One of the major contributors to greenhouse gas production is the final stage of anaerobic fermentation in the rumen (i.e. stomach compartment) of cattle, which produces methane. The process is the top agricultural source of greenhouse gases worldwide. In addition, the formation of methane is associated with approximately 10% energy loss in animals.

To ameliorate the dangers of methanogenesis, scientists at Washington State University explored the potential of homoacetogenic microbes (i.e. those that promote the production of acetate),  and especially Acetobacterium woodii, to outcompete methanogens and thereby reduce methane production in the rumen of production animals.

For this purpose, original inoculum of rumen samples were obtained from freshly slaughtered cows and developed into stable consortia of methanogens. Meanwhile, homoacetogenic cultures were developed from baby kangaroo droppings obtained from a wallaby ranch in Washington State. The original baby kangaroo sample had no methanogens present. Rumen bioreactors were inoculated with the bovine study samples and kangaroo gut microbes, and monitored for methane production and kinetics.

The investigators reported that acetogens are dominant in kangaroos, and in their presence methanogens are generally inhibited. The researchers suggested that kangaroos have interesting novel acetogens that utilize hydrogen, which rumen fermentation produces. These acetogens are potential probiotics, once they are well characterized and the benefits to rumen fermentation are documented.

This study also suggests that a variety of kangaroo acetogens should be further explored for their potential use in controlling rumen fermentation and reduction of greenhouse gas production. At the same time, additional benefits of acetogens from other marsupials could be explored and new findings are possible for potential biotic (pro-, pre-, syn- and postbiotic) development.

 

 

 

 

 

Clarifying the role of metabolites in the postbiotic definition

By Dr. Gabriel Vinderola PhD, Instituto de Lactología Industrial (CONICET-UNL), Faculty of Chemical Engineering, National University of Litoral, Santa Fe, Argentina and and Prof. Colin Hill PhD, School of Microbiology and APC Microbiome Ireland, University College Cork, Cork, Ireland

ISAPP published a definition for the term postbiotics in 2021 that states that “a postbiotic is a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host” (Salminen et al., 2021). This 19-word definition had to distill the content of the accompanying article that ran to over 9,000 words (not including references) and so obviously a lot of nuance was lost. A reading of the full paper should dispel any misconceptions, but we thought it might be timely to discuss what is perhaps the most common misunderstanding.

Some of the previous definitions included metabolites (purified or semi-purified) under the postbiotic concept. We did not agree with this interpretation. For us, the term postbiotics refers to preparations that consist largely of intact microbial cells, or preparations that retain some or all of the microbial biomass contained in microbial cells. This latter concept was captured in the phrase “and/or their components” The first column of page 3 of Salminen et al., 2021 elaborates on this; “The word ‘components’ was included because intact microorganisms might not be required for health effects, and any effects might be mediated by microbial cell components, including pili, cell wall components or other structures. The presence of microbial metabolites or end products of growth on the specified matrix produced during growth and/or fermentation is also anticipated in some postbiotic preparations, although the definition would not include substantially purified metabolites in the absence of cellular biomass. Such purified molecules should instead be named using existing, clear chemical nomenclature, for example, butyric acid or lactic acid”. So, taken in context, the scope of the ISAPP definition covers inanimate, dead, non-viable microbes; either as intact whole dead cells or in the form of “their components”. We do not consider microbial metabolites to be postbiotics. Such an interpretation would, for example, make butyrate or other end-products of fermentation postbiotics (once shown to have a health benefit). The ISAPP definition does not exclude the likelihood that microbial metabolites will be present in a postbiotic preparation, but it does require that dead microbes or microbial cell fragments or structures should be present to qualify as a postbiotic.

Why did the ISAPP definition exclude purified or semi-purified metabolites in the absence of cellular components? We fully accept that metabolites or other microbe-generated functional ingredients such as lactate, butyrate, bacteriocins, defensins, neurotransmitters, and similar compounds can be present in a postbiotic preparation. But as you can see from this list, these compounds already have names that are clearly understood. The ISAPP definition of postbiotics focuses on the beneficial role of inanimate microbes and/or their components, a category that did not have a clear definition. Postbiotics are simply one category of substances that provide microbe-associated health benefits. In terms of semantics, dictionaries define the prefix ‘post’ as meaning ‘after’ and the word ‘biotic’ as meaning ‘living things’, and so a postbiotic in that context is something that was living and is now after-life, or inanimate. Metabolites are derived from living things, but never had an independent ‘life’ of their own. As a thought experiment, let us imagine a microbe that has been shown to have a health benefit and therefore qualifies as a probiotic. If the same microbe is inactivated and continues to show a health benefit, this new formulation is no longer a probiotic and qualifies as a postbiotic. If this postbiotic preparation can be further purified and it is shown that a metabolite or metabolites in the absence of cells or their components can provide the same health benefit it ceases to be a postbiotic and becomes a health-promoting metabolite. We could imagine microbially-produced vitamins as an example.

Ideally, definitions should be clear without supplemental explanation. But short, simply worded definitions that describe complex concepts must be read in a context. There is a background, they have a scope, there are things that are covered by that definition and things that are not, and of course definitions have their limitations. It would be hard, if not impossible, to include the scope, the background, the coverage and the limitations in a 19-word definition. For instance, the 15-word probiotic definition is “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host” (Hill et al, 2014). This does not include the idea that probiotics are strain-dependent, a fact that is widely accepted by the field. Other criteria for probiotics not stated in the definition include the fact that that they may be of any regulatory category, that their health benefits must be demonstrated in well-controlled trials in the target host, and that they must be safe (Binda et al. 2020).

In closing, we believe that the postbiotic concept can be an incredibly important scientific, regulatory and commercial concept. That is why we spent the time and effort to arrive at what we hope is a workable definition. We accept that the definition is not perfect but we do think it is useful, and we urge those interested in the future of this important field to read the accompanying paper carefully and to place the definition in its proper context.

See ISAPP’s Postbiotics infographic here.

 

Postbiotics: debate continues and the ISAPP definition gains support

By Dr. Gabriel Vinderola PhD, Instituto de Lactología Industrial (CONICET-UNL), Santa Fe, Argentina

The publication of a new definition for the term “postbiotics” by ISAPP in 2021 (Salminen et al., 2021a) spurred discussion on a variety of platforms, including scientific journals, social media and in-person debates organized at industry and scientific meetings. A couple of months after the publication of the definition, a group of scientists expressed their disagreement about the new definition (Aguilar-Toalá et al., 2021), and this was followed by a reply in support of the ISAPP definition (Salminen et al., 2021b). An example of the debate on social media is reflected in this post on LinkedIn. The comments that followed the post highlighted points of disagreement and misunderstandings about the ISAPP definition. These reactions were helpful to me in preparing for panels and debates scheduled at 2023 meetings in Amsterdam, Chicago and Bratislava, discussed more fully below.

Prior to the ISAPP panel, many terms were used to refer to non-viable microorganisms that confer a health benefit when administered in adequate amounts: heat-killed probiotics, heat-treated probiotics, heat-inactivated probiotics, tyndallized probiotics, ghost-probiotics, non-viable probiotics, paraprobiotics, cell fragments, cell lysates or postbiotics. ISAPP proposed that going forward, the single term “postbiotic” be used in scientific communications, marketing, regulatory frameworks and to counter the difficulty in tracking of papers for comprehensive systematic reviews. ISAPP’s goal was to bring focus and clarity to the term postbiotic, provide criteria for proper use of the term and set the stage for future innovation in the field.

Two competing terms

When considering preparations of non-viable microorganisms that confer a health benefit, two terms seem to have emerged most dominantly:

The term paraprobiotic was coined by Taverniti and Guglielmetti (2011) and defined as non-viable microbial cells (intact or broken) or crude cell extracts (i.e. with complex chemical composition), which, when administered (orally or topically) in adequate amounts, confer a benefit on the human or animal consumer.

The term postbiotic as proposed by Salminen et al. (2021a) refers to a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.

The definition of paraprobiotics is limiting in that it does not clarify the scope for metabolites to be present alongside non-viable cells, and this may be problematic as most products of this type developed and marketed so far contain microbial metabolites along with non-viable cells. Further, the definition of paraprobiotics refers to conferring a benefit, but not a health benefit, a divergent way of conceptualizing a ‘biotic’ substance. Probiotics, prebiotics, synbiotics, and as defined above, postbiotics, all stipulate the requirement of conferring a health benefit. In addition, embedding the term ‘probiotic’ into the term paraprobiotic may mislead some to conclude that a paraprobiotic is a dead probiotic, which places a significant burden on any live microbial precursor to first meet the probiotic definition.

Finally, the authors (Taverniti and Guglielmetti 2011) state in their paper: “In addition, once a health benefit is demonstrated, the assignation of a product into the paraprobiotic category should not be influenced by the methods used for microbial cell inactivation, which may be achieved using physical or chemical strategies, including heat treatment, or UV ray deactivation, chemical or mechanical disruption, pressure, lyophilisation or acid deactivation”. Since inactivation technology may have a significant impact on the functionality of a dead microbe, disassociating a paraprobiotic with the method used to inactivate the microbes makes it impossible to know if any given paraprobiotic preparation will be effective.

The definition of postbiotics by Salminen et al. (2021a) anticipates that metabolites may be optionally present in the finished product, requires a health benefit and does not suggest, at any point in the wording, that the progenitor strain of a postbiotic must be a probiotic. Further, although not explicitly stated in the definition, the supporting documentation for the proposal of this definition states that the process to make the postbiotic must be delineated specifically, the progenitor microorganism must be clearly identified and characterized and the final product must be safe for its intended use. This definition encompasses a meaningful and useful scope.

To add to the complexity of the existing landscape, prior to the ISAPP definition of postbiotics, six other definitions of the term postbiotic were proposed in the literature. While these are reviewed in detail in Salminen et al (2021b Supplementary information), many shared the commonality that their focus was bacterial byproducts or metabolites.

Questions about the ISAPP definition of postbiotic

A common question is, “Why did the ISAPP panel choose the term postbiotic to refer to inactivated microbes?” In short, the word seemed most appropriate since post means ‘after’ and biotic means ‘life’.  Further, the panel recognized that although microbial metabolites might contribute to the health benefit conferred by a postbiotic, a preparation containing metabolites alone could be encompassed by a different term. Further, such metabolites (to the extent they are purified from the microbes that produce them) are readily referred to by their chemical names. Microbial metabolites may be present in a postbiotic preparation, but they are not required. The core of the definition of postbiotics is non-viable microbes, either as whole intact cells, disrupted cells or cell fragments. The life termination technology used to manufacture a postbiotic preparation should be stipulated. It cannot be assumed that heat inactivation, radiation, high pressure or any other technology will necessarily render an equally functional inanimate microbe.

Why use the descriptor “inanimate”? This is another common question. This word – meaning lifeless – reflects that the microorganisms should be dead, non-viable, no longer able to grow, to replicate, or, from an applied point of view, to form visible colonies in an enumeration medium or to be detected as live cells in flow cytometry techniques. It was preferred over the term “inactivated” only to call attention to the fact that postbiotics must confer a health benefit and in that sense, are active. For all practical purposes, non-viable can be used as an appropriate synonym.

Questions arise also about the breadth of definition, with concerns that “anything can be a postbiotic”. But broadness of a definition should not be seen as a disadvantage, as long as the limits to the definition are clear. Any microorganisms may be used as a postbiotic, as long as the identity is provided to the strain level, a life termination process is deliberately applied and safety and efficacy are demonstrated in a trial in the target host. Further, a postbiotic is not simply a dead probiotic. A probiotic is shown to confer a health benefit alive and it cannot be assumed that this property is retained when it is dead. Clearly, not anything can be a postbiotic.

Reflections on three recent conferences where the concept of postbiotics was debated

The first debate took place at the Beneficial Microbes conference in Amsterdam in November 2022. The outcomes were reported in a previous blog.

The second panel discussion took place in Chicago, at the Probiota 2023 conference in mid-June. After my talk, an audience poll was taken. Seventy-six out of around 250 attendees voted by an app in their cell phones to the question, How do you define a postbiotic? 68% selected the ISAPP definition, 9% said postbiotics were metabolites produced by probiotics, 4% chose the option “metabolites produced by the gut microbiota”, 14% said “none of the above” (I was curious to know what it would be for them), whereas 4% were not sure. Thus, the ISAPP definition was preferred by the majority. It is interesting to note the composition of the panel debate: three industry representatives and myself. Two of the companies represented presently market products referred to as postbiotics and containing non-viable microbes, whereas for the third company, postbiotics are “molecules created by bacteria”, according to their webpage. A discrepancy in the industry towards what postbiotics are was embodied on the stage. The preference for these meeting participants for the term postbiotic over the term paraprobiotic could be deduced from the meeting program, as the first term was mentioned 56 times, while the second had not one entry.

At Probiota 2023, an officer from Health Canada announced that the regulatory body will start considering the term postbiotics, which was defined in his presentation using the ISAPP definition. As for the quantification units for postbiotics, he indicated that milligrams would be considered currently, although he anticipated the development of more refined methodologies. The topic of what and how to quantify postbiotics is a commonly heard question. I intend to lead a Discussion Group on this topic comprising academic and ISAPP member company representatives at the 2024 ISAPP meeting July 9-11 in Cork, Ireland. If you are an academic expert or an industry member interested in joining the discussion, please reach out to me at gvinde@nullfiq.unl.edu.ar.

Panel discusson on postbiotics at the Bratislava International Probiotic Conference, 2023

A third panel discussion took place late in June in Bratislava at the 16th edition of the International Probiotic Conference. Before the debate, presentations were made by Arthur Ouwehand (IFF Health, Finland), Wilbert Sybesma (Yoba For Life Foundation, The Netherlands) and Eva Armengol (AB-BIOTICS, Spain). These speakers presented examples of postbiotics as they perceived them, which in all cases referred to administered non-viable microbes, in most cases containing microbial metabolites, thereby fitting the ISAPP definition. The fourth speaker, Simone Guglielmetti, proposed separate terms for non-viable microbes, which he proposed to call paraprobiotics, and for metabolites, which he proposed to call postbiotics, according to previous definitions (Taverniti and Guglielmetti, 2011; Tsiliringi and Rescigno, 2013).

There was also a sense of agreement that definitions should encompass current science but not unduly restrict future innovation. Some examples of products presently available in the market that contain non-viable microbes, and have efficacy studies with a clinical endpoint or biomarker enhancement, are:

 

Species or strain/s Composition Reference
B. bifidum MIMBb75 Heat inactivated bacteria https://pubmed.ncbi.nlm.nih.gov/32277872/
Akkermansia muciniphila Heat inactivated bacteria https://pubmed.ncbi.nlm.nih.gov/31263284/
L. fermentum CNCM MA65/4E-1b and L. delbrueckii CNCM MA65/4E-2z Heat inactivated bacteria plus metabolites https://pubmed.ncbi.nlm.nih.gov/33281937/
B. breve C50 and S. thermophilus 065 Heat inactivated bacteria plus metabolites https://pubmed.ncbi.nlm.nih.gov/32629970/
Aspergillus oryzae Heat inactivated fungi plus metabolites https://pubmed.ncbi.nlm.nih.gov/33742039/
L. paracasei MCC1849 Heat inactivated bacteria plus metabolites https://pubmed.ncbi.nlm.nih.gov/33787390/
L. sakei proBio65 Bacterial lysate plus metabolites https://pubmed.ncbi.nlm.nih.gov/32949011/
S. cerevisiae Heat inactivated yeasts plus metabolites https://pubmed.ncbi.nlm.nih.gov/21501093/
Vitreoscilla filiformis Bacterial lysate plus metabolites https://pubmed.ncbi.nlm.nih.gov/34976852/
Mixture of pathogens Bacterial lysate plus metabolites https://pubmed.ncbi.nlm.nih.gov/34976852/

 

These ten examples of commercial products based on non-viable microbes all fit the definition of postbiotics conceptualized by Salminen et al. (2021). Only the first two fit the Taverniti and Guglielmetti (2011) definition, as these contain just non-viable microorganisms, without metabolites. This may suggest that products in the current marketplace are best described by the Salminen et al. (2021) concept, which encompasses products based on non-viable microbes, which may or may not also contain microbial metabolites.

Conclusions

In conclusion, I suggest that the term postbiotic and the definition of Salminen et al. (2021a) be used for non-viable microbes (with or without metabolites) able to confer a health benefit, as reflected by the present state of the art and products developed and marketed. If deemed useful by the field, there is room yet for a new term to encompass products developed with microbial metabolites only (devoid of cells). If we consider definitions that mutually exclude non-viable microbes or metabolites, then the vast majority of products present today in the market would not be covered, as most of them deliver non-viable microorganisms and metabolites simultaneously. My overall sense after attending the Chicago and Bratislava meetings is that the meaning of the term postbiotic as mentioned by speakers, included in the meeting programs, seen in posters (future products) and in commercial products presented in booths, refers to the ISAPP definition of non-viable microbes. Time will tell how this term and definition evolves and if a broader consensus can be reached.

 

References

Aguilar-Toalá, J. E., Arioli, S., Behare, P., Belzer, C., Berni Canani, R., Chatel, J. M., D’Auria, E., de Freitas, M. Q., Elinav, E., Esmerino, E. A., García, H. S., da Cruz, A. G., González-Córdova, A. F., Guglielmetti, S., de Toledo Guimarães, J., Hernández-Mendoza, A., Langella, P., Liceaga, A. M., Magnani, M., Martin, R., … Zhou, Z. (2021). Postbiotics – when simplification fails to clarify. Nature reviews. Gastroenterology & hepatology18(11), 825–826. https://doi.org/10.1038/s41575-021-00521-6

Salminen, S., Collado, M. C., Endo, A., Hill, C., Lebeer, S., Quigley, E. M. M., Sanders, M. E., Shamir, R., Swann, J. R., Szajewska, H., & Vinderola, G. (2021a). The International Scientific Association of Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics. Nature reviews. Gastroenterology & hepatology18(9), 649–667. https://doi.org/10.1038/s41575-021-00440-6

Salminen, S., Collado, M. C., Endo, A., Hill, C., Lebeer, S., Quigley, E. M. M., Sanders, M. E., Shamir, R., Swann, J. R., Szajewska, H., & Vinderola, G. (2021b). Reply to: Postbiotics – when simplification fails to clarify. Nature reviews. Gastroenterology & hepatology18(11), 827–828. https://doi.org/10.1038/s41575-021-00522-5

Taverniti V, Guglielmetti S. The immunomodulatory properties of probiotic microorganisms beyond their viability (ghost probiotics: proposal of paraprobiotic concept). Genes Nutr. 2011 Aug;6(3):261-74. doi: 10.1007/s12263-011-0218-x. Epub 2011 Apr 16. PMID: 21499799; PMCID: PMC3145061.

Tsilingiri K, Rescigno M. Postbiotics: what else? Benef Microbes. 2013 Mar 1;4(1):101-7. doi: 10.3920/BM2012.0046. PMID: 23271068.

Can we use fermented foods to modulate the human immune system?

By Dr. Paul Gill PhD, Monash University

Fermented foods have grown in popularity in recent years, marketed for their purported health effects, including on the gut microbiome and immune system. Many of us have had a family member or friend recommend to us kombucha or sauerkraut based on a claim of curing their ailments. However, a reliable recommendation goes beyond anecdotal evidence and the science of how fermented foods confer any health benefits is often poorly understood. We often associate health effects of fermented foods with bacteria such as lactobacilli or Bifidobacterium, but what is lesser known is the role of microbial metabolites. These have sparked recent interest, particularly amongst researchers.

Many fermented foods naturally contain a mixture of live microorganisms and metabolites, such as phenolic compounds and short-chain fatty acids (SCFA). All of these components have the potential to impact host immunity, through two main mechanisms. Firstly, by directly interacting with local gut immune cells that have receptors for bacterial components such as lipopolysaccharide or peptidoglycan. Secondly, by modulating gut microbiota composition or function that will lead to indirect changes to host immunity. Together, these mechanisms are important for regulation of gut barrier integrity and immune homeostasis. Furthermore, bacterial metabolites such as SCFA are also absorbed by the portal vein and reach peripheral circulation, suggesting that they may also play a role in regulating systemic immune responses.

Although many of these findings are based upon observations from in vitro studies or pre-clinical models, several pilot studies in humans have also reported similar effects. A recent trial in a small cohort of healthy people found that consumption of an average of six servings of fermented foods per day for 10 weeks was associated with reduced serum inflammatory markers. Furthermore, consumption of a diet that included three servings of apple cider vinegar each day for three weeks, increased levels of plasma short-chain fatty acids and reduced subsets of circulating lymphocytes in a group of 20 healthy people. Taken together, these studies highlight the potential anti-inflammatory effects of fermented foods and postbiotics.

It remains a challenge to attribute consumption of fermented foods to alterations in host immunity, particularly due to the complex nature of these foods. This is particularly the case for traditional fermented food products that are not well characterised. After isolation and identification of individual metabolites within fermented foods, characterisation of how these compounds are absorbed and interact within the body is also necessary to determine how frequently they should be consumed to have meaningful effects on the immune system. Future studies need to be designed of sufficient duration, with a realistic dietary intervention and optimal timing of biological sampling is crucial to validate observations from exploratory trials. Finally, studies in patients with immune deficiencies will be needed to assess safety and potential therapeutic benefit. Alternatively, studies in healthy people during an immune challenge, such as during vaccination, are another desirable approach to investigate immune and therapeutic effects of fermented food consumption.

The scientific and medical communities, alongside the food industry, are continuing to improve our understanding of how fermented foods may benefit our health and immune system, including which components are responsible for any health benefits. Future studies are still needed to confirm if these may be of therapeutic benefit, and who may benefit the most from consuming these products. As our knowledge evolves, it is important that we continue to follow expert groups such as ISAPP to keep well informed and correctly communicate this information to patients and the public.

New global guidelines for probiotics and prebiotics for gut health and disease

By Mary Ellen Sanders, PhD, Executive Science Officer, ISAPP

The use of probiotics and prebiotics in the practice of gastroenterology must be guided by evidence – and with new evidence continually emerging, clinicians can benefit from efforts to summarize this evidence and determine how it applies in clinical practice.

In February 2023, the World Gastroenterology Organisation provided an updated resource in this area, titled “WGO Practice Guideline. Probiotics and Prebiotics”. This project was led by Prof. Francisco Guarner MD PhD, a clinical gastroenterologist and clinical researcher in probiotics and prebiotics, and brought together experts in gastroenterology, pediatrics, family medicine, probiotics, and prebiotics. Prof. Hania Szajewska MD PhD, a clinical pediatrician and clinical researcher in probiotics from the Medical University of Warsaw, was integral to assessing evidence for pediatric populations for the guidelines. Mary Ellen Sanders PhD co-chaired the project.

For 2023 update, 800 bibliographical entries of papers published in the 2017-2021 period were scrutinized. The review team adopted the guidelines for evaluation of probiotics established by FAO/WHO experts in 2002, where at least one double blind, randomized, placebo-controlled human trial with appropriate sample size and primary outcome is required to determine if the tested product is efficacious, and qualifies as a probiotic.

ISAPP was well-represented among the experts involved on the project, as four current board members contributed. In addition to Sanders and Szajewska, Prof. Dan Merenstein MD (current ISAPP president) and Prof. Seppo Salminen PhD (current past president) populated the team.

The Guideline is intended to provide specific information on interventions that may have benefit for indicated conditions. Recommendations included probiotics or prebiotics found in at least one randomized, controlled trial showing benefit. Trials that did not show benefit were not included. The Guideline serves an important role in informing gastroenterologists around the world, especially in regions where product availability might be limited. Especially useful are Tables 8 and 9, which summarize evidence for adult and pediatric uses, respectively.

Guarner states, “We hope our WGO guideline will assist doctors, pharmacists, dietitians and other healthcare professionals all around the world to integrate probiotics and prebiotics in an evidence-based manner into their daily work of patient care.”

The Guideline provides text that introduces current understanding of probiotics and prebiotics and then comprehensively evaluates the evidence for gastrointestinal conditions. Evidence is graded from 1-3, with Level 1 referring to evidence supported by systematic review of randomized trials, Level 2 supported by randomized trials with consistent effect, without systematic review, and Level 3, supported by a single randomized controlled trial, as per the Oxford Centre for Evidence-Based Medicine.

The 2017 iteration of these guidelines was available in six languages (English, French, Portuguese, Mandarin, Russian and Spanish). This guideline is the most accessed guideline title on the WGO website,  accounting for nearly one-quarter of all visits to the site. The 2023 version is only available in English so far, but translations are underway.

Clinical conditions for which some evidence was found include:

  • Diarrheal conditions: acute, antibiotic-associated, difficile-associated, radiotherapy-associated, enteral nutrition-associated, nosocomial,
  • Diverticular disease
  • Functional abdominal pain
  • Functional constipation
  • Insulin resistance
  • Health-related quality of life
  • Helicobacter pylori infection
  • Hepatic encephalopathy
  • Infantile colic
  • Inflammatory bowel disease
  • Irritable bowel syndrome
  • Lactose maldigestion
  • Nonalcoholic fatty liver disease
  • Nonalcoholic steatohepatitis
  • Necrotizing enterocolitis

 

About WGO:
World Gastroenterology Organisation (WGO) is a federation of over 100 Member Societies and four Regional Associations of gastroenterology representing over 60,000 individual members worldwide.  The WGO Guidelines Library contains practice guidelines written from a viewpoint of global applicability. The Guidelines go through a rigorous process of authoring, editing, and peer review and are as evidence based as possible.

Are the microbes in fermented foods safe? A microbiologist helps demystify live microbes in foods for consumers

By Dr. Gabriel Vinderola, PhD,  Associate Professor of Microbiology at the Faculty of Chemical Engineering from the National University of Litoral and Principal Researcher from CONICET at the Dairy Products Institute (CONICET-UNL), Santa Fe, Argentina.

Since very early in my career I was drawn to science communication. I feel that rather than just producing my own results, silently in my lab, I can extend the reach of the science by amplifying other people’s work. At least in the southern cone where budgets for research have been always limited, science communication is a way to be active in science.

Before the pandemic I used my Instagram account mostly to share personal moments with my circle of family and friends. But when the COVID-19 pandemic hit, I saw interest in fermented foods skyrocket. I started sharing tips about how to prepare fermented foods, telling the science behind them, separating myths from facts, making Instagram Live videos with fermentationists, nutritionists, pediatricians and gastroenterologists, and I turned my personal Instagram account into a public one with an outreach of more than 100,000 followers (@gvinde), from Mexico down to Argentina.

During the pandemic, people were largely homebound and concerned about staying healthy.  The idea of healthy food to keep a diverse gut microbiome that had the potential to enhance our gut and respiratory immune systems against coronavirus really resonated with people. I even had the chance to participate in several radio and TV programs discussing these topics as well as making yoghurt, kefir, kombucha, sauerkraut and sourdough bread at home. I saw that people had the time to devote part of their days at home to keep these communities of microbes “cooking” for them. But these activities revealed to me that more people than I realized did not know that we can eat microbes in a safe way and that they may actually be good for us.

In my encounters, I found much confusion about fermented dairy products. People believe that dairy products must be kept refrigerated, but at the same time they see ultrapasteurized milk, powdered milk or hard cheeses marketed at room temperature. People find it difficult to understand why pasteurized milk should go in the refrigerator but not unopened ultrapasteurized milk.

Some hesitancy around bacterial safety exists because Argentina leads the world in annual cases of Uremic Hemolitic Syndrome (UHS), a life-threatening condition for children, especially those under the age of 5 years, caused by shiga-toxin producing Escherichia coli. Almost 400 children get sick in Argentina every year due to UHS. Among other recommendations, pediatricians tell parents not to offer their children unpasteurized dairy products. This leads to the the most common question I receive on Instagram from parents worried about yoghurt safety: Is yoghurt pasteurized?  “No!” I emphasize. “Yoghurt is not pasteurized, but it is made out of pasteurized milk. In fact, yoghurt has viable bacteria.” And this is when the panic begins.

If yoghurt has live bacteria, then can’t any bacteria grow there, even the bacteria responsible for UHS? If I leave yoghurt outside the refrigerator or in my car too long, won’t this make it more likely that the UHS bacteria will grow?” This is where I try to use an army of arguments to communicate science in the simplest possible way, from more philosophical to more science-based facts.

The first thing I share is that fermentation was invented well before refrigerators. Fermentation was used by people to preserve foods, for periods well longer than the time it takes to take the yoghurt from the supermarket to make it home or than the time a yoghurt sits in the backpack of my child waiting for school lunchtime. I once posted that I ate a yoghurt that was left in my car for one whole day. That generated a lot of debate on social media!

Then I inform them that the fermentation process to make yoghurt causes the pH to drop well below values needed for pathogens to grow. That it is highly unlikely that a pathogen can enter a well-sealed yoghurt, and in the event that it would be possible, the acidic conditions would impair the pathogen from growing to a level that could be life-threating.

People not only worried about yoghurts bought in the supermarket, well-sealed and made under the strictest safety conditions in industry. In the pandemic many parents learned how to make yoghurt at home, and they wanted to know how safe it is. In these cases, I advised the following to assure their homemade yogurt was safe: use a yoghurt from the supermarket to launch your own fermentation, use pasteurized milk, use good quality water to wash your kitchen devices, and wash your hands properly. In addition you can use a domestic pHmeter or pH indicators to make sure pH dropped below 4.5. In a successful fermentation – after about 1 gallon sitting 8-12 hours at a warm temperature – the fluid milk will transform into a gel. If not, you should discard it.

If these arguments are not enough, then I draw their attention to the well-respected product milk kefir. At least in this region, kefir is surrounded by a halo of “something that is good, no matter what”. People are familiar with the process of fermenting milk kefir at room temperature for a full day. So I make this comparison: commercial yoghurt is fermented for 6 hours, then it is refrigerated and taken to the supermarket. If you are OK letting milk kefir ferment for a whole day, shouldn’t yogurt sitting without refrigeration for a few more hours be harmless enough? It likely would only get more acidic because bacteria will resume fermentation. This fermented food would not become a life-threatening food in just a couple of hours. If milk kefir does not in 24 hours, why should yoghurt?

To further argue, I comment that kombucha is fermented at room temperature for 10 days, sauerkraut for 2 weeks and kimchi for several months. And they are all consumed with their microbes alive. They key is that the microbes that flourish make the environment inhospitable to pathogens.

Still I feel that there is a lot of uncertainty among consumers about the safety of fermented foods and this is may be an obstacle to making them more popular. Scientists must meet the challenge to communicate to lay audiences about how to make fermented foods safely at home and how to store them so they are safe. Nothing is ever 100% safe, but the small risks associated with fermented foods are greatly outweighed by the enjoyment of making and consuming fermented foods.

 

Additional reading:

Suggestions for Making Safe Fermented Foods at Home

2022 TEDx talk

2021 Teaching how to make kefir on TV during the pandemic

2019 participation in Argentina’s most famous TV show, featuring the same host for more than 50 years non-stop

Horse with rider.

Probiotic Use in Horses: What is the Evidence?

By Kelly S. Swanson, PhD, The Kraft Heinz Company Endowed Professor in Human Nutrition, University of Illinois at Urbana-Champaign, USA

Horses play a special role in many people’s lives, serving as a partner in leisure activities, therapy, various forms of work, and athletic competitions. Being large herbivores, they are adapted to a diet rich in grasses and other high-fiber forages. The complex community of microbes inhabiting the hindgut (cecum and colon) is necessary for the efficient breakdown of these fibers as well as maintaining the gastrointestinal health and overall health of horses. In recent years, a lot has been learned about the composition and activity of the gastrointestinal microbiota of horses and their role in health and disease (Kauter et al, 2019). There has also been interest in testing whether yeast- or bacteria-based probiotics may help manage equine health and disease.

Is there evidence supporting probiotic use in horses? The answer depends on the animal’s life stage, dietary and exercise strategy, and health status.

Probiotics for foals

A common target of probiotic use has been young growing foals. Similar to other host species, the gastrointestinal microbiota population of foals has a lower diversity and stability than that of adult horses (Earing et al., 2012; De La Torre et al., 2019). This instability makes foals more susceptible to pathogen-induced microbiota alterations, diarrhea, dehydration, and intestinal inflammation (Frederick et al., 2009; Schoster et al., 2017; Oliver-Espinosa, 2018). But probiotic use in foals has had both helpful and harmful outcomes. Positive results were obtained with a probiotic containing 5 Lactobacillus strains (L. salivarius YIT 0479, L. reuteri YIT 0480, L. crispatus YIT 0481, L. johnsonii YIT 0482, L. equi YIT 0483), which were shown to increase body weight and reduce diarrhea incidence in 3-4 week old foals (Yuyama et al., 2004). Similarly, a probiotic composed of 4 Lactobacillus strains (L. reuteri KK18, L. ruminis KK14, L. equi KK15, L. johnsonii KK21) and 1 Bifidobacterium strain (B. boum HU) was reported to reduce the incidence and duration of diarrhea in foals during their first 5 months of life (Tanabe et al., 2014). However, administration of a different probiotic (L. pentosus WE7) was associated with anorexia, development of diarrhea, and greater need for veterinary examination and treatment (Weese and Rousseau, 2005). Based on the evidence thus far, caution should be used when considering probiotic use in foals.

Probiotics for adult horses

Even though adult horses have a more stable and rich gastrointestinal microbiota than young animals, microbiota disruptions can occur with rapid changes in diet, transportation stress, the onset of gastrointestinal disease, or other diseases such as laminitis or grass sickness (Garrett et al., 2002; Costa et al., 2012; Moreau et al., 2014). Horses are susceptible to gastrointestinal disorders such as enterocolitis that may be due to antibiotic use, stressful conditions, or pathogen infection (e.g., Clostridioides difficile; Salmonella). Not all probiotic interventions have led to improvements, but there are examples of success. In one study, a Saccharomyces boulardii treatment reduced the severity and duration of illness in horses with acute enterocolitis (Desrochers et al., 2005). In another study, a probiotic mixture of 3 Lactobacillus strains (of the species L. plantarum, L. casei, L. acidophilus) and 1 Enterococcus strain (E. faecium) reduced the incidence of Salmonella shedding in horses admitted for routine medical and surgical treatments (Ward et al., 2004). Overall, there is weak evidence for probiotic use in horses with enterocolitis at this time.

In healthy adult horses, the reasons for using probiotics may differ depending on the fiber and starch content of the diet being fed. In horses fed a high-fiber diet composed of grasses and hay, live yeast cultures (Saccharomyces cerevisiae) have increased nutrient breakdown and energy extraction (Medina et al., 2002; Jouany et al., 2008; Garber et al., 2020). Such increased efficiency may be helpful for horses eating low-quality forages or performance animals that have higher energy requirements. To meet the energy needs of many high-energy or performance animals, grains that are rich in starch and have a higher energy content are often fed. A high-starch diet helps meet the energy requirement, but if not managed properly, it can exceed the capabilities of the horse’s small intestine, resulting in significant starch loads entering the hindgut. These starches are highly fermentable by hindgut microbiota, resulting in the rapid production of lactic acid and short-chain fatty acids. The accumulation of these acids can lead to hindgut acidosis and diseases such as colic or laminitis. Lactobacilli have been shown to modify equine microbiota populations, decreasing amylolytic bacteria and increasing lactic-acid utilizers, and ultimately attenuating starch breakdown and pH decline ex vivo (Harlow et al., 2017). Live yeast cultures have also been shown to help attenuate the hindgut lactic acid concentrations and maintain the hindgut pH of horses fed high-starch diets (Medina et al., 2002). These studies suggest that probiotics may be useful in increasing the digestive efficiency and/or maintaining the hindgut homeostasis of healthy adult horses.

Probiotics for horse athletic performance

Because probiotics have been used to support exercise performance in humans (Pyne et al., 2015), similar interventions have been tested in performance horses recently. In one study a probiotic mixture of 5 Lactobacillus strains (L. acidophilus DSM 32241, L. plantarum DSM 32244, L. casei DSM 32243, L. helveticus DSM 32242, L. brevis DSM 27961), 2 Bifidobacterium strains (B. lactis DSM 32246, B. lactis DSM 32247)), and 1 Streptococcus strain (S. thermophilus DSM 32245) reduced post-exercise blood lactate concentrations and modified blood and urinary metabolite profiles (Laghi et al., 2018). In another study, a probiotic mixture of 2 Lactobacillus strains (from the species L. plantarum and L. paracasei) increased blood oxygen saturation and reduced blood lactic acid concentrations (Zavistanaviciute et al., 2019). Because lactic acid production and accumulation results in fatigue and reduced performance, these studies suggest that probiotics may support athletic performance in horses. The results of these studies are promising, but more research is necessary.

State of the science

Data to support use of probiotics in horses is emerging, but the occurrence of harmful outcomes in at least one study reinforces the need for high quality studies that can precisely establish efficacious conditions and formulations for use. Similar to recommendations for other host species, equine probiotics should provide an effective dose, be designed for horses, target a specific life stage and condition, and be supported by evidence. It is important to remember that probiotic efficacy can depend on specific microbial strains, supplement form, storage conditions, and dosage  – see ISAPP’s infographic ‘What Qualifies as a Probiotic’ for more details on probiotics.

Kelly Swanson joined the ISAPP board of directors in June, 2020, providing valuable expertise in animal gut health and overall health. Swanson also chaired the 2019 ISAPP-led international consensus panel on the definition of synbiotics.

How metabolites help us to understand the effect of gut microbes on health

By Dr. Anisha Wijeyesekera, University of Reading, UK

Much literature relating to the gut microbiota has focused on microbial composition (for example, using culture-dependent and -independent molecular biology approaches). Composition is important; knowing which microbes are present in a community enables us to gain insight into population dynamics and how these may be affected by disease, lifestyle and environmental factors (including diet). However, composition does not provide information on microbial function, and considering the gut contains the most metabolically active microbial community in the whole body, it is thus equally as important to be able to answer the question “what are the microorganisms doing”? This is of particular importance with respect to better understanding the impact of dietary interventions such as prebiotics, probiotics and other ‘biotics on health, where health benefits conferred on the host are mediated via the gut microbiota.

Investigating microbial function

Advances in phenotypic analytical technologies (for example, high-throughput sequencing, biochemical analysis, as well as bioinformatics and other multivariate data analysis approaches), have resulted in a stepwise change in our understanding of microbial function. Metabolic phenotyping (also referred to as metabolomics, metabonomics or metabolic profiling) is an exciting field in systems biology that provides information on the multiple metabolic mechanisms taking place in a system, at a given moment in time (see here). This top-down approach enables high-throughput detection and quantification of low molecular weight molecules present in a biological sample at the time of sampling, without a priori knowledge of metabolites present. Hence, it is ideally suited to augment and complement information obtained from microbial profiling approaches such as metataxonomics, to gain deeper insight into microbial function.

Metabolic phenotyping is conducted by applying analytical chemistry technologies (typically, 1H-nuclear magnetic resonance spectroscopy, and/or mass spectrometry often with chromatographic separation techniques such as gas chromatography and liquid chromatography (for prior separation of molecules followed by detection)) to capture a biochemical snapshot of a sample. In human samples (e.g. urine, blood plasma/serum and stool), metabolites detected using metabolic phenotyping are low molecular weight molecules and include intermediate and end by-products of endogenous host metabolic pathways (e.g. TCA cycle, amino acid metabolism), but also exogenous signals arising from diet, drugs and other lifestyle and environmental stimuli, including products of microbe-host co-metabolism, which provide insight into host-gut microbiota interactions. These include short-chain fatty acids (predominantly acetate, butyrate and propionate, which have a key role in host energy metabolism), bile acids (involved in the gut-liver axis), biogenic amines (involved in the gut-brain axis) and vitamins. Metabolic phenotyping, which provides functional assessment of the gut microbiota and captures information on microbial metabolic activity following ‘biotics intervention, can aid in forming hypotheses about microbial activity that may lead to health benefits.

Challenges in determining the functions of microbes

Nevertheless, functional assessment of the microbiota remains analytically challenging. For example, human metabolic phenotypes contain information relating to different forms of optically active isomers, such as lactate and amino acids (where D- forms originate from bacteria). These enantiomers cannot be differentiated using standard metabolic phenotyping experiments, and it would be important particularly in studies identifying potential biomarkers of disease, to understand the origin of these compounds. Hence, we and others have also conducted mechanistic studies using in vitro human gut model systems (e.g. the model developed by Macfarlane et al., 1998, which  has been validated against gut contents from sudden death victims and give a very close analogy to bacterial activities and composition in different areas of the hindgut), Metabolic screening of fermentation samples using metabolic phenotyping approaches provides a unique opportunity to capture dynamic microbial metabolism that is reflective of the gut microbiome in vivo, and removes contributions derived from host physiological processes (see here).

Unravelling the close interplay between microbes and host, using approaches such as metabolic phenotyping, not only provides insight into host-gut interactions, but aids our understanding of the alterations in gut microbiota mediated mechanisms that result in disease, and which demonstrate potential as therapeutic targets. More research in this area will aid in deepening understanding of the role of the gut microbiota in health and disease, and aid in the design of interventions targeting the gut microbiota (for example, the development of functional foods) for therapeutic benefit.

Food of the future: Fermented and sustainable

By Dr. Mary Ellen Sanders, ISAPP Executive Science Officer

An exciting research initiative at the crossroads of fermented foods and sustainable diets is underway. Funded by the EU and Switzerland, and coordinated by KU Leuven in Belgium, HealthFerm is a 4-year, 13.1 MM € project involving 23 partners from 10 countries. Prof. Christophe Courtin, KU Leuven, serves as the overall project coordinator.

HealthFerm seeks to understand how to transition toward more sustainable, healthy diets through leveraging fermented foods and technologies. Its overall aim is to understand the interaction between food fermentation microbiomes, fermented plant-based foods, the human gut microbiome and human health. Many information gaps will be addressed by the project, which is organized around six work projects that are designed to integrate basic research, intervention studies, fermentation technology, consumer behavior and communication strategies.

Scientific perspectives on fermented food is at the heart of HealthFerm. Fermented foods were defined in an ISAPP consensus paper as ‘foods made through desired microbial growth and enzymatic conversions of food components’. Predating ancient Egyptian society, fermented foods and beverages are thought to have originated over 8000 years ago, and today over 5000 varieties are enjoyed around the globe, contributing substantially to human nutrition. Fermented foods have many advantages over the raw materials from which they are made, including improved sensory characteristics, safety and stability as well as potential health benefits. How the live microbial components of fermented foods may drive the health benefits of fermented foods is an active area of research.

Prof. Courtin shares some of his thoughts about HealthFerm.

Why focus on fermentation as a means of attaining more sustainable diets?

Courtin: When considering a sustainable diet, we automatically look at replacing part of our animal-based foods with plant-based foods. But plant biomass is often less functional and more recalcitrant than animal-based materials. Look for example at the whipping behavior of egg proteins or the availability of iron. Getting more out of plant fiber through fermentation is also a point of attention. In short, we believe that fermentation can help us functionalize plant materials and make it more nutritious.

 

Fermented foods have been around a long time. Why do you think now is the time to leverage their benefits?

Courtin: Societies are increasingly interested in fermented foods for a large number of reasons. We want to leverage that. From a scientific point of view, state-of-the-art omics-technologies coupled with bioinformatics allow us to look in depth into food microbiomes better than ever before and use them in a targeted way to functionalize plant materials. In addition, they also allow performing human intervention trials and doing relevant analyses to understand if and how fermented foods can improve human health, focusing on the gut microbiome and cardiometabolic health.

 

Looking ahead, what is your greatest hope for the project?

Courtin: I hope we can come to a rational design of new fermentation processes and products for the crops we target (faba bean, yellow pea, wheat, oats), using microbial resources we mobilize in collaboration with citizens and companies through community science projects. I also hope we get clear results and mechanistic insights from the intervention trials on the effects of consuming fermented foods and diets.

 

ISAPP is represented on the HealthFerm Stakeholder Board, which convened its first meeting January 20, 2023.

 

Looking back and looking ahead: ISAPP session focuses on the past, present, and future of the biotics field

Kristina Campbell, MSc, and Prof. Dan Tancredi, PhD, Professor of Pediatrics, UC Davis School of Medicine and Center for Healthcare Policy and Research

Twenty years ago, in 2002, the first ISAPP meeting was held in London, Canada. At the time, the field was much less developed: only small human trials on probiotics or prebiotics had been published, no Nutrition and Health Claims legislation existed in the EU, and the human microbiome project hadn’t been conceived.

Now in ISAPP’s 20th year, the scientific landscape of probiotics and prebiotics is vastly different. For one thing, probiotics and prebiotics now form part of the broader field of “biotics”, which also encompasses both synbiotics and postbiotics. Hundreds of trials on biotics have been published, regulations on safety and health claims has evolved tremendously globally, and ”biotics” are go-to interventions (both food and drug) to modulate the microbiota for health.

At the ISAPP annual meeting earlier this year, scientists across academia and industry joined together for an interactive session discussing the past, present and future of the biotics field. Three invited speakers set the stage by covering some important advancements in the field. Then session chair (Prof. Daniel Tancredi) invited the participants to divide into 12 small groups to discuss responses to a set of questions. The session was focused on generating ideas, rather than achieving consensus.

The following is a summary of the main ideas generated about the past, present and future of the biotics field. Many of the ideas, naturally, were future-focused – participants were interested in how to move the field of biotics forward with purpose.

The past 20 years in the biotics field

Prof. Eamonn Quigley had the challenge of opening the discussion about the past by summing up the last 20 years in the biotics field. He covered early microbiological progress in the biotics field, such as the production of antimicrobials and progress in understanding the biology of lactic acid bacteria and their phages. In the modern era, scientists made strides in understanding the role of gut bacteria and metabolites in hepatic encephalopathy; the role of C. difficile in pseudo-membranous colitis; and in the 90s, the concept of bacterial translocation in the intestines. Prof. Quigley summarized the progress and challenges in advancing the underlying science and in developing actionable clinical evidence. He noted that more high-quality clinical trials are being published lately.

The discussion participants noted the following achievements in the field over the past two decades:

Recognition that microbes can be ‘good’. A massive shift in public consciousness has taken place over the past 20 years: the increased recognition that microorganisms are not just pathogens, they have a role to play in the maintenance of health. This added impetus to the idea that consuming beneficial microbes or other biotics is desirable or even necessary.

The high profile of biotics. An increasing number of people are familiar with the basic idea of biotics. Especially for probiotics, there is a strong legacy of use for digestive health; they are also widely available to consumers all around the world.

ISAPP’s published papers. Participants appreciated the papers published as a result of ISAPP’s efforts, including the five scientific consensus definition papers. These have raised the profile of biotics and clarified important issues.

Connections between basic and clinical scientists. Collaborations between biotics scientists and clinicians have been increasing over the past two decades, leading to better questions and higher quality research. ISAPP is one of the leading organizations that provides opportunities for these two groups to interact.

These were among the challenges from the past two decades, as identified by discussion participants:

Lack of understanding among those outside the probiotic/prebiotic field. Although the science has advanced greatly over the past 20 years, some outside the biotics field continue to believe the evidence for probiotic efficacy is thin. It appears some early stereotypes about probiotics and other biotics persist, especially in some clinical settings. This also leads to consumer misunderstandings and affects how they use biotics substances.

Too many studies lacking in quality. In the past, many studies were poorly designed; and sometimes the clinical research did not follow the science. Further, a relative lack of mechanistic research is evident in the literature.

Lack of regulatory harmony. Probiotics and other biotics are regulated in different ways around the world. The lack of harmonized regulations (for example, EFSA and FDA having different regulatory approaches) has led to confusion about how to scientifically substantiate claims in the proper way to satisfy regulators.

Lack of standardized methodologies. Many scientific variables related to biotics, such as microbiome measurements, do not have standardized methodologies, making comparability between studies difficult.

Not having validated biomarkers. The absence of validated biomarkers was noted as a potential impediment to conducting feasible clinical research studies.

The current status of the biotics field

At the moment, the biotics field is more active than ever. The industry has grown to billions of dollars per year and microbial therapeutics are in development all across the globe. The number of published pro/prebiotic papers is over 40K and the consensus definitions alone have been accessed over half a million times.

Prof. Kristin Verbeke spoke at the interactive session about the biotics field at present. She noted that the field has faced the scientific reality that there is no single microbiota configuration exclusively associated with health. The current trajectory is to develop and expand systems biology approaches for understanding the taxonomic and functional composition of microbiomes and how those impact health. Scientists are increasingly making use of bioinformatics tools to improve multi-omic analyses, and working toward proving causation.

The future of the biotics field

Prof. Clara Belzer at the ISAPP 2022 annual meeting

Prof. Clara Belzer spoke on the future of the biotics field, focusing on a so-called “next-generation” bacterium, Akkermansia muciniphila. She covered how nutritional strategies might be based on improved understanding of the interplay between microbes and mucosal health via mucin glycans, and the potential for synthetic microbial communities to lead to scientific discoveries in microbial ecology and health. She also mentioned some notable citizen science education and research projects, which will contribute to overall knowledge in the biotics field.

Participants identified the following future directions in the field of biotics:

Expanding biotics to medical (disease) applications. One group discussed at length the potential of biotics to expand from food applications (for general overall health) to medical applications. The science and regulatory frameworks will drive this shift. They believed this expansion will increase the credibility of biotics among healthcare practitioners, as the health benefits will be medical-condition-specific and will also have much broader applicability.

As for which medical conditions are promising, the group discussed indications for which there are demonstrated mechanistic as well as clinical effects: atopic diseases, irritable bowel syndrome, and stimulating the immune system to boost vaccine efficacy. In general, three different groups of medical conditions could be targeted: (1) common infections, (2) serious infectious diseases, and (3) chronic diseases for which drugs are currently inadequate, such as metabolic disorders, mental health disorders and autoimmune diseases.

Using biotics as adjuncts to medical treatments. An area of huge potential for biotics is in complementing existing medical treatments for chronic disease. There is evidence suggesting in some cases biotics could be used to increase the efficacy of drugs or perhaps reduce side effects, for example with proton pump inhibitors, statins, NSAIDs, metformin, or cancer drugs. Biotics are not going to replace commonly used drugs, but helping manage certain diseases is certainly within reach.

Using real-world data in studies. Participants said more well-conducted studies should be done using real world data. This seems in line with the development of citizen science projects as described by Clara Belzer and others at the ISAPP meeting. Real-world data is particularly important in the research on food patterns/dietary habits as they relate to biotics.

Considering new probiotic formulations. In some cases, a cocktail of many strains (50-60, for example) may be necessary for achieving a certain health effect. Using good models and data from human participants, it may be possible to create these multi-strain formulations with increased effects on the gut microbial ecosystem and increased efficacy.

Embracing omics technology and its advancement. Participants thought the next five years should see a focus on omics data, which allows for stratifying individuals in studies. This will also help increase the quality of RCTs.

More mechanism of action studies. Several groups expressed the importance of investing in understanding mechanisms of action for biotic substances. Such understandings can help drive more targeted clinical studies, providing a rationale for the exact type of intervention that is likely to be effective. Thus, clinical studies can be stronger and have more positive outcomes.

Increased focus on public / consumer engagement. Educational platforms can engage consumers, providing grassroots support for more research resources as well as advancing regulatory frameworks. Diagnostic tools (e.g. microbiome tests with validated recommendations) will help drive engagement of consumers. Further, science bloggers are critical for sharing good-quality information, and other digital channels can have great impact.

Defining and developing “precision biotics”. One group talked about “precision biotics” as solutions that target specific health benefits, which also have a well-defined or unique mechanism of action. At present, this category of biotics is in its very early stages; a prerequisite would be to better define the causes and pathways of gastrointestinal diseases.

Increasing incentives for good science. Participants discussed altering the regulatory and market environments so that good science and proper randomized, controlled trials on biotics are incentivized. Regulators in particular need to change their approaches so that companies are driven primarily by the science.

Precise characterization of responders and non-responders. The responder and non-responder phenomenon is seen with many biotic interventions. Across the field, deep characterization of subjects using multi-omics approaches with a high resolution is needed to determine what factors drive response and non-response to particular biotics substances.

Overall, participants’ ideas centered around the theme of leaning into the science to be able to create better-quality biotics products that support the health of different consumer and patient groups.

 

Special thanks to the table discussion leaders: Irene Lenoir-Wijnkoop, Zac Lewis, Seema Mody, David Obis, Mariya Petrova, Amanda Ramer-Tait, Delphine Saulnier, Marieke Schoemaker, Barry Silkington, Stephen Theis, Elaine Vaughan and Anisha Wijeyesekera.

Picture of panelists on stage with conference participants in the audience

Definition of postbiotics: A panel debate in Amsterdam

By Dr. Gabriel Vinderola, PhD,  Associate Professor of Microbiology at the Faculty of Chemical Engineering from the National University of Litoral and Principal Researcher from CONICET at the Dairy Products Institute (CONICET-UNL), Santa Fe, Argentina.

A panel debate titled “Postbiotics, definition and scopes” was convened at the 9th Beneficial Microbes conference in Amsterdam on November 14, 2022. The aim of this panel was to advance the discussion about postbiotics in the aftermath of some published disagreement (see here and here) about the definition of postbiotics produced and published by ISAPP: “a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host”. The debaters included Prof. Seppo Salminen and myself (Dr. Gabriel Vinderola), both members of the board of directors of ISAPP and co-authors of the ISAPP postbiotics definition, supporting the ISAPP definition, and Prof. Lorenzo Morelli (in attendance virtually) and Dr. Guus Roeselers challenging the ISAPP definition. The debate was attended by around 150 persons, and consisted of 15-minute opening arguments on both sides, followed by a 30 min open discussion guided by the conference chair, Dr. Koen Venema.

I introduced ISAPP as a non-profit organization dedicated to advancing the science on probiotics, prebiotics and related substances. Among many other activities, ISAPP has produced 5 different consensus definitions: probiotics, prebiotics, synbiotics, postbiotics and fermented foods. Each consensus panel was composed of academic scientists with different backgrounds, expertise and perspectives, comprising at least 11 authors from 4 – 10 countries, who came together to incorporate broad perspectives and engage in thoughtful debate. To date, all 5 consensus papers have had almost half a millon accesses at Nature Reviews Gastroentetology and Hepatology, the journal where all of the definitions are published.

The discussion within ISAPP about the need for a postbiotic definition dates back to our 2019 annual meeting. Emerging research on the health benefits conferred by non-viable microbes, their fragments and metabolites was discussed at the meeting, and this planted the seed for a definition that would cover this area. Many different terms such as heat-killed probiotics, heat-treated probiotics, heat-inactivated probiotics, tyndallized probiotics, paraprobiotics, ghost probiotics, cell fragments, cell lysates and postbiotics had been used to encompass these substances.

The panel discussed these different terms and previously published definitions. Those opposed to the ISAPP definition preferred the Tsilingiri and Rescigno (2013)1 definition of postbiotics, which focuses on metabolites produced by probiotics. I reviewed the limitations of that definition, which were outlined in Salminen et al. (2021)2. One concern is that requiring a postbiotic to be derived from a probiotic creates an unnecessary burden of first meeting the criteria for a probiotic before developing a postbiotic.

Morelli emphasized the importance of definitions for regulatory bodies and stated that researchers should provide guidance on criteria to meet a definition. He quoted the first published definition of postbiotic by Tsilingiri and Rescigno in 20131: “any factor resulting from the metabolic activity of a probiotic or any released molecule capable of conferring beneficial effects to the host in a direct or indirect way”. Morelli stated that one value of this definition was that it was clear to regulators; metabolites are measurable and produced by microbes already accepted as food components with a long history of safe use. He considered this of paramount relevance as otherwise, the novel foods path would be required. He challenged the ISAPP approach as defining a substance that was unclear how to measure. Morelli showed pictures depicting the deterioration of the biomass of freeze-dried cultures during storage, to underscore the challenges of controlling the quality of products based on biomass of non-viable microbes. He added, “If we don´t know which are the components responsible for the health benefits, then it is challenging to determine what to measure.” He questioned the ability to establish the shelf life of such a product. The need to be precise in terms of how to quantify the active components of non-viable cells was essential to his criticism of ISAPP’s definition of postbiotics. Prof. Morelli concluded that researchers must address this issue of quantification methods, both to advance research and to provide regulatory bodies needed approaches to regulating non-viable microbes.

Conclusions from the debate were that the flaws of definitions previous to the ISAPP definition are apparent, and that the substance defined by ISAPP was useful to delineate, but that clear approaches to measurement of the active component(s) of non-viable microbes are needed to make the ISAPP definition workable in scientific and regulatory circles. The debate was very worthwhile, since science advances through respectful debates such as this.

It is clear that characterization of postbiotic products may be challenging, especially with increased complexity that arises by use of multiple inanimate strains, inclusion of  metabolic  endproducts, and the presence of whole and fragmented cells. But these challenges are not unique to postbiotics. Probiotic products can comprise complex mixtures of multiple strains as well as metabolic products (as the biomass during industrial production is harvested for freeze-drying, but not washed), along with significant amounts of non-viable microbes, which all may contribute to the overall health benefit. These facts are usually overlooked when relying just on viable cells for quantification.

Many commercial products carrying inanimate microbes and metabolic fermentation products, that potentially fit the ISAPP definition of postbiotics, are already available in the market. These are diverse products such as a mixture of two lactobacilli aimed at treating infant and adult diarrhea3 or a fermented infant formula to support pediatric growth4. Similar products also target animal nutrition5. A tightly controlled manufacturing process may be the path forward to warrant reproducibility of health benefits. Suitable characterization methodologies such as flow cytometry for non-viable microbes and mass spectrometry for metabolites seem to be relevant to sufficient postbiotic product characterization.

In brief, the ISAPP definition itself seemed well accepted by the meeting participants, but concerns were raised about how to quantify postbiotics according to the definition. We intend to address this point through consultations with experts, proposing scientific paths to help conceptualize factors that need to be considered for postbiotic quantification.

Picture of panelists on stage with conference participants in the audience

Panel debate about ISAPP’s definition of postbiotics held at Beneficial Microbes conference in Amsterdam on November 14th, 2022. On the stage, from left to right: Koen Venema (conference chair), Gabriel Vinderola, Seppo Salminen, Guus Roeselers and Lorenzo Morelli (on screen).

References

  1. Tsilingiri, K. & Rescigno, M. Postbiotics: What else? Benef. Microbes (2013) doi:10.3920/BM2012.0046.
  2. Salminen, S. et al. The International Scientific Association of Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics. Nat. Rev. Gastroenterol. Hepatol. (2021) doi:10.1038/s41575-021-00440-6.
  3. Malagón-Rojas, J. N., Mantziari, A., Salminen, S. & Szajewska, H. Postbiotics for Preventing and Treating Common Infectious Diseases in Children: A Systematic Review. Nutrients 12, (2020).
  4. Béghin, L. et al. Fermented infant formula (with Bifidobacterium breve C50 and Streptococcus thermophilus O65) with prebiotic oligosaccharides is safe and modulates the gut microbiota towards a microbiota closer to that of breastfed infants. Clin. Nutr. 40, 778–787 (2021).
  5. Kaufman, J. D. et al. A postbiotic from Aspergillus oryzae attenuates the impact of heat stress in ectothermic and endothermic organisms. Sci. Rep. 11, 6407 (2021).

Additional reading:

Follow up from ISAPP webinar – Probiotics, prebiotics, synbiotics, postbiotics and fermented foods: how to implement ISAPP consensus definitions

Postbiotics: The concept and their use in healthy populations

 

Watch / listen to the debate here: https://youtu.be/pATNfhQY4P4

 

 

The many functions of human milk oligosaccharides: A Q&A with Prof. Ardythe Morrow

Human milk is the ‘gold standard’ of infant nutrition—and some scientists have set their sights on working towards that standard to improve the health of infants who are not breastfed. Among the many important components of human milk are human milk oligosaccharides (HMOs): complex carbohydrates that are 3-32 sugars in length. Over 200 different HMO molecules have been discovered, but a mother typically has between 12 and 20 in her milk. Some types of HMOs are affected by genetic polymorphisms – for example, only those who have the FUT2 (secretor) gene have breast milk containing HMOs called 2′-fucosylated (2’-FL) glycans.

ISAPP held a webinar in October, 2022 featuring Prof. Ardythe Morrow, University of Cincinnati College of Medicine, speaking about the latest research on HMOs and their health effects in both infants and adults.

HMOs as prebiotics

Prof. Morrow emphasized that research to date on HMOs shows they clearly fit the scientific consensus definition for prebiotics: a “substrate that is selectively utilized by host microorganisms conferring a health benefit”. HMOs are utilized by bacteria in the infant gut—mainly bifidobacteria, but also other genera (Yu, Chen & Newburg, 2013)—producing end-products that benefit infant health. B. longum subsp. infantis are the quintessential bacteria that grow on HMOs; pathogens do not typically grow on them.

Within the prebiotic category, HMOs are unique. Unlike other prebiotic substances they are structurally similar to gut oligosaccharides, which populate the surface of mucosal surfaces of the GI tract and are abundant in the mucin layer. They also can function via mechanisms that do not require utilization by gut microbes.

Beyond prebiotic function

Prof. Morrow emphasized that HMOs are multi-functional agents: in addition to their prebiotic functions, they have direct functions in the infant gut that are not mediated by microbes. First, individual HMOs have been shown to bind pathogens and inhibit infections and bind to immune cells to optimize their function (Triantis, Bode & van Neerven, 2018). Further, they can enhance neurodevelopment and brain function (Furness, Kunze & Clerc 1999; Sharon et al, 2016). The latter is a more recent domain of research, but so far it is known that basic neurodevelopmental processes are modulated in animals that are germ-free or have a depleted gut microbiota.

Certain HMOs (notably 2’-FL) can be produced synthetically and are being tested in infant formulas, and more recently for healthy adults (Elison et al., 2016). Prof. Morrow noted HMOs also have potential as novel therapeutics for various indications, such as inflammatory bowel disease (IBD). Determining which specific HMOs are most effective in these outcomes, and the dose needed, is an active area of research.

The webinar participants generated some interesting questions, some of which Prof. Morrow answers below.

Are 2’FL and LNnT (Lacto-N-neotetraose) found in cow’s milk?

2′-FL is not found in cow’s milk. Other oligosaccharides, especially sialyl oligosaccharides, are present but generally at very low levels.

How similar to HMOs are the glycosylation patterns on gut mucin?

Mucin glycosylation is not identical to human milk. But there are structural motifs that recur in both milk and gut mucin.

Do the more abundant HMOs have more potential for health benefit, compared with those at lower abundances in human milk?

We do not know that more abundance means more functionality or importance. But it is a reasonable place to start with the research. Also, several of the most abundant HMOs are trisaccharides (2’FL, 3FL, 3′-SL, and 6′-SL), and these are the most manageable to synthesize and start with.

For non-secretors, HMO complexity in milk is around 30% lower than for secretors. Does this factor affect the beneficial functions of non-secretor HMOs?

Having lower HMO content might be an issue in some circumstances. But we cannot say that it is a general problem. Furthermore, if non-secretors have more sialyloligosaccharides and 3-FL instead of 2′-FL, for example, perhaps this helps protect against viruses that bind to sialic acid epitopes (for example, influenza). Or perhaps this helps with increasing sialic acid to the brain (see Mudd et al., 2017). So, my argument is that at this point in our knowledge, we should avoid any idea of “superior” or “inferior” milk for the general healthy public. More likely, there are situation-specific benefits or disadvantages for different milk oligosaccharide phenotypes.

What do you think is more important for infant formula, more HMO complexity or more structure-function relations?

A set of HMOs for normal infant nutrition will be important, and these include fucosyllactoses, sialyllactoses, and neutral oligosaccharide with neither sialic acid nor fucose. Structure-function orientation is important to guide use in special populations with specific health needs.

Long term, will HMOs replace FOS and GOS in infant formulas?

All of the efforts in making infant formula have the goal of doing the best possible job of mimicking the physiological function of breastmilk, but cost and function are also relevant factors to consider in this process. It’s important that babies get some form of prebiotic. GOS is structurally more similar to HMOs, but it’s not enough on its own. Ideally, we’d hope for a rational mixture of different oligosaccharides backed by research confirming their combined functions.

Can we really replicate HMOs with synthetic formula, given the large number of diverse HMOs present in human milk?

I do not foresee ever achieving full replication, no. But getting closer to mother’s milk, yes, over time.

How is the dosing of HMOs in clinical trials for adults being determined? Should it be based on human milk concentration?

Elison et al. published a dosing study based on tolerance and shift of microbiota. A dosing study is now underway in Cincinnati, too.

Since it is fairly difficult to manufacture HMOs, do you think they provide sufficient advantages compared to GOS to justify their use as prebiotics in adults?

We do not yet know whether HMOs might have enough advantage over GOS in some situations, or whether prebiotic combinations might be best. This is research in progress! The reason for testing 2′-FL in IBD is because of the structure-function evidence. IBD is increased in non-secretors, and is associated with dysbiosis, inflammation, and so on. We will learn from the ongoing research.

Do you think adults will differ in response to HMOs therapeutically, possibly based on genetic differences?

I don’t yet have data on this, but have a study ongoing that I hope will be able to address this very question.

 

Watch the recording of this webinar below:

 

 

 

 

Shaping microbial exposures and the immune system in childhood: Can sandboxes be probiotic?

By Prof. Seppo Salminen, University of Turku, Finland

Gut microbiota researchers have established that microbial exposures in early life can be influential on health later in life. Children who develop asthma in early childhood, for example, have an altered gut microbiota linked with exposure to less diverse microorganisms in their first year. The ‘biodiversity hypothesis’ has been advanced recently, suggesting that western lifestyles and low biodiversity in urban environments reduce contact with microbes both via food and via the natural environment, presenting fewer opportunities for children to be exposed to a diversity of microbes in their earliest years and increasing the risk of non-communicable diseases. If this is the case, the environments of daycare and kindergarten facilities come under scrutiny as a source of microbial exposures at a crucial time of life. So is it beneficial to intervene in children’s environments to ensure more diverse microbial exposures? Can we enhance gut microbial diversity and richness in children through environmental interventions?

A new study provided proof that shaping children’s microbial exposures may be possible. The study was the first of its kind – a placebo-controlled, double-blinded study on the effect of environmental exposures on gut microbiota diversity and immune parameters in young children. The study used playground sandboxes at daycare facilities as sources of environmental microbial diversity and explored whether these could have effects on the children.

Six day-care centers in southern Finland were enrolled in the study, with two randomly assigned to intervention and four to placebo. Identical-looking playground sandboxes were used. Intervention sandboxes were filled with sand of glacial origin enriched with a known biodiversity powder (including commercial soil, deciduous leaf litter, peat, and Sphagnum moss; described in detail by Hui et al., 2019 ; Grönroos et al, 2018). In control centers the sand was regular sandbox sand and placebo peat material. Altogether, 26 children ages 3-5 participated in supervised play for 20 minutes in the morning and afternoon for two weeks. Researchers measured the composition of gut and skin microbiota, as well as blood immune markers.

The results demonstrated that exposure to diverse environmental microbiota enhanced both the bacterial richness and diversity of the skin bacterial community. The microbiome of the skin changed only in those children who had played in a sandbox enriched with natural materials. The authors also found that the daily exposure to higher microbial biodiversity resulted in positive differences in immune response. For instance, the authors reported shifts in skin microbiota associated with IL-10 and T cell frequencies. This provides the first evidence from a placebo-controlled, double-blinded study in young children showing the differential effects on microbiota and immunity of daily exposure to defined microbial biodiversity.

An interesting follow-up could be using sandboxes to deliver probiotics with a proven health impact to children. Since the sandbox microbes were shown to influence children’s immune systems, could researchers go one step further and modulate children’s microbiota in a targeted manner? A probiotic must be defined, shown to have a health benefit and administered in an efficacious dose. In the case of sandboxes, the health benefit would need to be demonstrated for a certain level or duration of environmental exposure.

Playgrounds and sandboxes require materials that tolerate heavy wear and tear and are safe at the same time. Such materials need to be kept free of unnecessary contamination as sandboxes, for example, can also be good reservoirs of some detrimental bacteria. Therefore, it could be important to have defined natural materials for a positive impact on health. In the future, we may see many creative approaches to ensuring children receive appropriate health-supporting microbial exposures early in life. However, creating probiotic approaches requires identification of specific microbes in the biodiversity powder.

Why researchers need to understand more about the small intestinal microbiome

By Prof. Eamonn M. M. Quigley, MD, The Methodist Hospital and Weill Cornell School of Medicine, and Prof. Purna Kashyap, MD, Mayo Clinic

The phrase “gut microbiota” properly refers to the microorganisms living throughout the entire digestive tract, including the mouth and the upper digestive tract, through the length of the small intestine as well as the large intestine. Yet the vast majority of scientific studies on the gut microbiota make conclusions based only on stool samples, meaning that the contributions to health and disease of microorganisms from most of the digestive tract are largely unexplored.

Researchers have established that the microorganisms throughout different parts of the digestive tract vary greatly. In particular, the microorganisms living in the small intestine are fewer in number than those in the colon. They are less diverse, and they change more over time because of their dynamic environment (fluctuations in oxygen, digestive secretions, dietary substrates, among other influences).

The dynamic composition and biologic functions of the small intestinal microbiome in health and disease are mostly unknown. Research has been hampered by the difficulty in obtaining samples from this area of the digestive tract and, in particular, its more distal reaches. Participants in a 2022 ISAPP discussion group argued, however, there are some good reasons to dedicate more effort to investigation of the small intestinal microbiome:

  • The small intestine has critical homeostatic functions in relation to nutrient digestion and absorption, immune engagement and interactions with the enteric and central nervous systems, as well as the neuroendocrine system. Each of these could be influenced by microbiota-host interactions. Important locations for these interactions include the gut barrier and mucosa- or gut-associated lymphoid tissue. The nature of microbiota-host interactions in these particular areas needs to be better understood, as they could have implications for systemic host health.
  • Diet plays a critical role in symptom generation in many gastrointestinal disorders; it is important to better understand diet-microbe interactions in the gut lumen to determine how the small intestinal microbiome may be contributing to diet-triggered symptoms.
  • A disordered small intestinal microbiome is commonly implicated in the pathogenesis of various gastrointestinal and non-gastrointestinal symptoms, from irritable bowel syndrome to Alzheimer’s disease, through the much-disputed concept of small intestinal bacterial overgrowth (SIBO). A precise definition of the normal small intestinal microbiome is a prerequisite to the accurate diagnosis of SIBO and linking it with various disease states.

How can we gain more information on the small intestinal microbiome? Our group tackled the limitations of current definitions and diagnostic methods, noting that this field may be advanced in the near future by new technologies for real-time sampling of intestinal gases and contents. The group discussed optimal methods for the sampling of small intestinal microbes and their metabolic products—noting that a full range of ‘omics technologies applied in well-defined populations could lead to further insights. In the meantime, the gastroenterologists in our group advised restraint in the diagnosis of SIBO and the need to exert caution in identifying it as the cause of symptoms. Clinical progress in this area is best achieved through the application of modern molecular methods to the study of human small intestinal microorganisms.

Are probiotics effective in improving symptoms of constipation?

By Eirini Dimidi, PhD, Lecturer at King’s College London

Constipation is a common disorder that affects approximately 8% of the general population and is characterised by symptoms of infrequent or difficult bowel movements (1). People who suffer with constipation often report that it negatively affects their quality of life and the majority use some sort of treatment, such as fibre supplements and laxatives, to alleviate their symptoms (2). However, approximately half of those report they are not completely satisfied with the treatment options currently available to them, mainly due to lack of effectiveness in improving their symptoms (2).

Could probiotics offer an effective alternative way to treat constipation symptoms?

Our team at the Department of Nutritional Sciences at King’s College London has investigated the potential benefits of probiotic supplements in chronic constipation. We have extensively reviewed the available evidence on their mechanisms of action in affecting gut motility and their effectiveness in improving symptoms, and we have also conducted a randomised controlled trial of a novel probiotic in 75 people with chronic constipation (3-5).

USE OF PROBIOTICS

Before looking at the evidence on the effectiveness of probiotics in constipation, it is easy to see that some people with constipation already choose to try probiotics for their gut health. A national UK survey of over 2,500 members of the public, which included people with and without constipation, showed that people with constipation have a 5.2 higher chance of currently using probiotics for gut health, compared to people who don’t suffer from it (3).

However, the majority of doctors do not recommend probiotics for the relief of constipation symptoms, nor do they believe there is enough evidence to support their use in this condition (3).

So, what is the current evidence on probiotics and constipation?

MECHANISMS OF ACTION OF PROBIOTICS

Probiotics may impact gut motility and constipation through several mechanisms of action. Depending on the strain, they may affect the number and composition of gut microbes, as well as the compounds they release. The gut microbiota and their released compounds can then interact with our immune and nervous system, with the latter being the primary regulator of gut motility, ultimately improving constipation symptoms. Therefore, there is a rationale to support a potential improvement in constipation. But is this supported by evidence from clinical trials?

EFFECTIVENESS OF PROBIOTICS

A systematic review of the literature showed Bifidobacterium lactis strains appear to improve several symptoms of constipation, such as infrequent bowel movements and hard stools (4). At the same time, other probiotic species did not improve any symptoms. This is an important finding as it highlights that not all probiotics have the same effects in constipation, and that only certain probiotics may improve constipation. Therefore, people with constipation may only benefit from specific probiotic products – but which products would those be? Since the systematic review above showed that several B. lactis strains were effective, does this means that people with constipation may benefit from any B. lactis-containing product?

Unfortunately, it is a bit more complicated. Since the publication of the aforementioned review, new studies have been published showing that, while some probiotic products with B. lactis are effective, various other B. lactis probiotics do not impact constipation (5-6). This may be explained by strain-specific effects, but also other methodological differences among studies (e.g. probiotic dose).

TAKE HOME MESSAGE

Can we recommend probiotics for the management of constipation? At the moment, there is some low quality evidence to support the use of certain Bifidobacterium lactis strains to help manage symptoms of constipation. Further high-quality studies are needed to clarify which specific probiotic strains may be effective. However, given that there is some evidence in this area (albeit limited), along with the fact probiotics are safe for the general population to consume (unless clinically contraindicated), people with constipation could try a probiotic product of their choice for four weeks, should they wish to, bearing in mind the uncertainty in the evidence so far. But scientists continue to work to answer this question because the evidence is promising enough to warrant continued study of probiotics for constipation.

 

    1. Palsson, Gastroenterol 2020;158:1262-1273
    2. Johanson & Kralstein, Aliment Pharmacol Ther 2007;25(5):599-608
    3. Dimidi et al, Nutrition 2019;61:157-163
    4. Dimidi et al, Am J Clin Nutr 2014;100(4):1075-84
    5. Dimidi et al, Aliment Pharmacol Ther 2019;49:251-264
    6. Wang et al, Beneficial Microbes 2021;12:31-42

 

 

Can diet shape the effects of probiotics or prebiotics?

By Prof. Maria Marco PhD, University of California – Davis and Prof. Kevin Whelan PhD, King’s College London

If you take any probiotic or prebiotic product off the shelf and give it to several different people to consume, you might find that each person experiences a different effect. One person may notice a dramatic reduction in gastrointestinal symptoms, for example, while another person may experience no benefit. On one level this is not surprising, since every person is unique. But as scientists, we are interested in finding out exactly what makes a person respond to a given probiotic or prebiotic to help healthcare providers know which products to recommend to which people.

Among factors that might impact someone’s response to a probiotic or prebiotic – such as baseline microbiota, medications, and host genetics – diet emerges as a top candidate. Ample evidence has emerged over the past ten years that diet has direct and important effects on the structure and function of the gut microbiome. Overall the human gut microbiome is shaped by habitual diet (that is, the types of foods consumed habitually over time), but the microbes can also can fluctuate in response to short-term dietary shifts. Different dietary patterns are associated with distinct gut microbiome capabilities. Since probiotics and prebiotics may then interact with gut microbes when consumed, it is plausible that probiotic activity and prebiotic-mediated gut microbiome modulation may be impacted by host diet.

A discussion group convened at ISAPP’s 2022 annual meeting brought together experts from academia and industry to address whether there is evidence to support the impact of diet on the health effects of probiotics and prebiotics. To answer this question, we looked at how many probiotic or prebiotic studies included data on subjects’ diets.

  • Prebiotics: Our review of the literature showed that only a handful of prebiotic intervention studies actively measured background diet as a potential confounder of the effect of the prebiotic. One such study (Healey, et al., 2018) classified individuals based on habitual fiber intake, and in doing so found that the gut microbiome of individuals consuming high fiber diets exhibited more changes to microbiome composition than individuals with low fiber intake. While both groups consuming prebiotics showed enrichment of Bifidobacterium, those with high fiber intake uniquely were enriched in numerous other taxa, including butyrate-producing groups of microbes. Prebiotics also resulted in improved feelings of satiety, but only among the high fiber diet consumers.
  • Probiotics: We found no evidence of published human RCTs on probiotics that investigated diet as a possible confounding factor. This is a significant gap, since we know from other studies that host diet affects the metabolic and functional activity of probiotic lactobacilli in the digestive tract. Moreover, the food matrix for the probiotic may further shape its effects, via the way in which the probiotic is released in situ.

Our expert group agreed that diet should be included in the development of new human studies on probiotics and prebiotics, as well as other ‘-biotics’ and fermented foods. These data are urgently needed because although diet may be a main factor affecting outcomes of clinical trials for such products, it is currently a “hidden” factor.

We acknowledge there will be challenges in taking diet into account in future trials. For one, should researchers merely record subjects’ habitual dietary intake, or should they provide a prescribed diet for the duration of the trial? The dietary intervention (nutrient, food, or whole diet) must also be clearly defined, and researchers should carefully consider how to measure diet (e.g. using prospective or retrospective methods). In the nutrition field, it is well known that there are challenges and limitations in the ways dietary intake is recorded as well as the selection of dietary exclusion criteria. Hence, it is crucial that dietitians knowledgeable in dietary assessment and microbiome research contribute to the design of such trials.

If more probiotic and prebiotic trials begin to include measures of diet, perhaps we will get closer to understanding the precise factors that shape someone’s response to these products, ultimately allowing people to have more confidence that the product they consume will give them the benefits they expect.