By Marla Cunningham, Metagenics Global R&D Innovation Manager and 2021 ISAPP Industry Advisory Committee representative
Let’s assume a hypothetical clinical study has been published with positive impacts of a yoghurt containing Lacticaseibacillus rhamnosus strain XYZ in children with atopic dermatitis. If the strain is now to be incorporated into a fruit drink, at the clinically trialled dose throughout shelf life, can it be expected to have the same health benefits? Can the probiotic yoghurt study provide primary support of efficacy claims on the probiotic fruit drink? Such a question is highly relevant to the challenges that food and supplement manufacturers within the ISAPP community face daily in product development.
This important scientific and regulatory question is addressed in a new ISAPP-driven collaborative article, originating from opinions and data presented at the industry-organised Learning Forum at the 2019 ISAPP annual meeting in Antwerp. The paper, published online April 21 in Trends in Food Science and Technology, reviewed preclinical and clinical evidence for an impact of product matrix on functionality of probiotics and prebiotics.
The article notes it is well-recognised that heat, pH and moisture are key factors causing degradation in probiotics and prebiotics, and such factors currently weigh heavily in formulation design and quality assurance processes for these products. Beyond such impacts on degradation, some evidence suggests that ingredients in the product matrix can affect probiotic and prebiotic functionality in vitro, for example via the binding of proteins or carbohydrates to structural components of prebiotics or altering activity of effector molecules on probiotics.
However, clinical trials do not provide convincing evidence that observed preclinical interactions are significant in vivo. Head-to-head clinical trials comparing product formats are rare, meaning that direct evidence that product formats can influence a clinical endpoint is lacking. To address this gap, researchers are encouraged to consider comparing different matrixes in future clinical trials. Yet, while differences in study factors (such as populations, interventions and doses) limit conclusions that can be drawn from comparing across clinical studies, meta-analyses in general suggest a robustness of effect across a broad range of delivery matrices for given clinical endpoints.
Preclinical assessments are useful, but limited. Attempts to replicate findings from highly controlled preclinical experiments often fail because preclinical assessments cannot capture the complexity of the physiology or the individual factors inherent to the human subject. It makes sense that any impact of physicochemical interaction between probiotics or prebiotics with a product matrix may not be revealed in vivo. If we consider the almost infinite number of variations that could make up a study subject’s (or consumer’s) diet, probiotics and prebiotics are in fact being delivered in a variety of matrices every day, with substantially greater potential for physiochemical interactions in the digestive tract outside of product formulation variables. Add to this interindividual differences in human physiology and microbiome, and the overall impact of product formulation differences on the expression of a clinical effect in an end consumer may be smaller still.
This broader perspective suggests that even if it were ethically and practically possible, unrestrained investment into the repetition of clinical trials for each new product format may not be the answer to provide a high degree of confidence for translation of clinical trial evidence to any given consumer. Instead, research dollars may be better spent in the short term on mechanistic and clinical studies investigating the relative impact of factors determining individual response to probiotic and prebiotic intervention, including factors intrinsic to the host as well the product formulation.
Nonetheless, it is critical that any extrapolation of evidence across product formats is supported by a solid scientific rationale. As such, the article provides recommendations for a practical path forward to demonstrate essential equivalence between product formats, utilising in vitro and in vivo tests, and clinical trials where justified. Such an approach is intended to provide reasonable assurance of scientific substantiation and may also go some way to meeting the expectations of regulatory authorities across the globe (reviewed within).
The open access article can be found here.