What you've heard: Probiotic pills fix your gut
Do probiotic pills fix your gut?
For healthy people, unsupported; spend the money on yogurt and beans. Evidence grade: Probable.
Published Updated
The "What you've heard" box in Chapter 6
For healthy people, unsupported; spend the money on yogurt and beans
The evidence
In a review of seven randomized trials, probiotic supplements did not change the diversity of healthy adults' gut microbes compared with a placebo. In one small study, a probiotic taken after antibiotics even slowed the gut's recovery. Gastroenterologists back specific probiotics only for narrow uses, such as helping prevent the gut infection C. difficile during antibiotics. The clearest proof that gut microbes matter comes from the opposite direction: a donor-stool infusion, given after antibiotics and a bowel wash, cured about four in five patients with recurrent C. difficile in one trial.9 A capsule of a few strains is a different thing.
Where the book tests it
Related claims
- Is raw milk healthier or safe?Against, and the risk is measured.Evidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.
- Can a greens powder replace vegetables?Expensive vitamins, and no substitute for vegetables.Evidence grade: Emerging. Early, small, animal-only, or actively contested.
- Is leaky gut real?Real in specific diseases, unproven as an everyday diagnosis.Evidence grade: Emerging. Early, small, animal-only, or actively contested.
Sources
The "What you've heard" box in Chapter 6
- 9.Kristensen, N.B., Bryrup, T., Allin, K.H., Nielsen, T., et al. (2016). "Alterations in fecal microbiota composition by probiotic supplementation in healthy adults: a systematic review of randomized controlled trials." Genome Medicine, 8(1), 52. https://doi.org/10.1186/s13073-016-0300-5; Suez, J., Zmora, N., Zilberman-Schapira, G., Mor, U., et al. (2018). "Post-antibiotic gut mucosal microbiome reconstitution is impaired by probiotics and improved by autologous FMT." Cell, 174(6), 1406-1423.e16. https://doi.org/10.1016/j.cell.2018.08.047; Su, G.L., Ko, C.W., Bercik, P., Falck-Ytter, Y., et al. (2020). "AGA clinical practice guidelines on the role of probiotics in the management of gastrointestinal disorders." Gastroenterology, 159(2), 697-705. https://doi.org/10.1053/j.gastro.2020.05.059; van Nood, E., Vrieze, A., Nieuwdorp, M., Fuentes, S., et al. (2013). "Duodenal infusion of donor feces for recurrent Clostridium difficile." New England Journal of Medicine, 368(5), 407-415. https://doi.org/10.1056/NEJMoa1205037 (donor stool after a short course of vancomycin and a bowel wash cured 13 of 16, against 4 of 13 on vancomycin alone)
Note numbers are those of Chapter 6, The Gut That Expects Dirt.
This verdict is one of the "What you've heard" boxes in Chapter 6, The Gut That Expects Dirt, where the book tests the claims people repeat against the studies behind them. The grade rates the evidence behind the verdict, by the book's stated method.
Educational content, not medical advice. Disclaimer.