Photo by http://benvandenbroecke.be/ Copyright, ISAPP 2019.
The scientific definition of the term ‘probiotic’ was proposed in a 2001 joint report of the Food and Agriculture Organization of the United Nations and the World Health Organization (FAO/WHO), and confirmed by an expert panel convened by ISAPP held in 2013. The currently accepted definition of probiotics is: “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”
Live microorganisms may be present in many foods and supplements, but only characterized strains with a scientifically demonstrated effect on health should be called probiotics. Live microbes present in traditional fermented foods and beverages such as kombucha, sauerkraut, and kimchi typically do not meet the required evidence level for probiotics, since their health effects have not been confirmed and the mixtures are largely uncharacterized.
Probiotics are known by genus, species, and strain: for example, Lactobacillus acidophilus ABC. The strain designation is important, as different strains of the same species may have different health effects. Dose is also a consideration, and a probiotic consumed at a higher dose may not necessarily have a greater health benefit than one consumed at a lower dose. The does should match the level shown in an efficacy study to confer a benefit.
Probiotic products (usually dietary supplements or foods) may be recommended for different conditions or symptoms an individual is experiencing. Decades of study on specific probiotic strains have revealed particular health benefits – however, remember that not all these benefits will be delivered by any one product:
- Helping reduce the incidence and duration of antibiotic-associated diarrhea
- Helping manage digestive discomfort (including in irritable bowel syndrome)
- Helping reduce colic symptoms in breastfed babies and occurrence of atopic issues such as eczema in infants
- Helping reduce necrotizing enterocolitis in preterm infants
- Helping reduce symptoms of lactose maldigestion
- Treating acute pediatric infectious diarrhea
- Decreasing the risk or duration of upper respiratory tract infections (such as the common cold) or gut infections
An increasing number of studies also support probiotic health benefits beyond the digestive tract: for oral care in children and for liver health, bacterial vaginosis, urinary tract infections, and other indications in adults.
A robust safety profile has been documented in clinical trials for many probiotic strains. However, for certain at-risk populations, such as premature infants, immunocompromised individuals, those with a serious illness, and those with ‘short gut’, a manuscript describing precautions has been published.
In some cases, probiotic mechanisms of action are known; in other cases, they are not even though a health benefit has been demonstrated. A common misconception is that probiotics need to alter the gut microbiota in order to be effective. In fact, probiotics are not known to take up permanent residence in the gut despite documented health benefits.