Probiotics

Do probiotics change your gut bacteria?

Updated 4 Nov 2026

Short answer

Only a little and for a short time in the studies so far, and it depends on the strain and the person. A review of 7 trials in healthy adults found no effect on the diversity, richness or evenness of stool bacteria. One trial found a change in the overall makeup.[1] In a study of an 11-strain mix, the microbes stayed alive through the gut. How well they settled differed by person, strain and gut region, and the effect was short.[2]

Sources (2)

  1. Alterations in fecal microbiota composition by probiotic supplementation in healthy adults: a systematic review of randomized controlled trials. Kristensen NB, Bryrup T, Allin KH, Nielsen T, Hansen TH, Pedersen O Genome Med, 2016. PMID 27159972
  2. Personalized Gut Mucosal Colonization Resistance to Empiric Probiotics Is Associated with Unique Host and Microbiome Features. Zmora N, Zilberman-Schapira G, Suez J, Mor U, Dori-Bachash M, Bashiardes S, et al. Cell, 2018. PMID 30193112

More about probiotics

What are probiotics?Is a higher CFU count better?Which foods contain probiotics?What are probiotics used for?Do probiotics prevent diarrhea from antibiotics and C. difficile?Are probiotics safe, and who should avoid them?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.