Probiotics — “good” bacteria that provide a health benefit to the humans who consume them — have been with us since the beginning. Since they are found naturally in fermented foods and breast milk, they constitute part of the ancestral human diet. However, the trend of commercial products that contain probiotics is a relatively new trend, and one that is growing.
According to the World Health Organization (WHO), probiotics are “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.” The rub is knowing whether or not there’s a proven health benefit. The mere presence of “billions of live organisms” does not confer a health benefit — not that you’d know that after browsing the aisles of a health food or high-end grocery store.
However, Jack Gilbert, director of the Microbiome Institute, points out the crux of the problem in his article in Nautilus: a dearth of research. “The lack of clinical trials demonstrating efficacy is the major obstacle to knowing whether [probiotics] are better than existing formulations that have been shown clinically to help with diarrhea and atopy. Claims that probiotic mixtures will help to support overall health are still woefully unproven.”
Furthermore, because the industry operates without any real regulatory oversight in the US, you can’t really be sure of what you’re getting. Multiple studies have found that there were discrepancies between the labelled ingredients and what was actually found in the product, and this problem was especially egregious among products containing multiple strains of bacteria. For example, an analysis of 16 probiotic products conducted in 2015 found that only one of the 16 products tested exactly matched its label for every sample tested.