priors.science/reviews/probiotics-and-gut-microbiome

Probiotics and Gut Microbiome

The current evidence on 7 claims, ordered from most established to most contested. Each score is the panel’s evidence certainty: how firmly the literature supports the claim as stated.

7claims tracked
127primary papers reviewed
4 Oct 2026latest evidence review
0 Established · 3 Likely · 2 Uncertain · 2 Doubtful  |  four-reviewer panel · PICO Framework
ClaimStandingEvidence certaintyCorpus
Probiotic colonization of adult gut is transientMicrobiomeLikely80%21
Probiotics reduce upper respiratory tract infection incidenceSystemicLikely77%17
Probiotics reduce irritable bowel syndrome symptom severityClinicalLikely70%18
Probiotics reduce depressive symptomsSystemicUncertain57%17
Probiotics prevent antibiotic-associated diarrheaClinicalLong-standingUncertain55%20
Probiotics prevent Clostridioides difficile infectionClinicalDoubtful40%12
Probiotics raise gut microbial diversityMicrobiomeDoubtful35%23
Track Probiotics and Gut Microbiome.
These claims are re-checked against new research as it is published. Track this topic for the full review, including each claim’s challenge and the papers behind it.
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Standing: what the evidence certainty means
Established≥ 85%Strong, consistent evidence. Unlikely to change.
Likely70–84%Well supported, with some gaps or indirect evidence.
Uncertain50–69%Mixed or limited evidence. Genuinely open.
Doubtful30–49%Little support; the weight of evidence leans against it.
Refuted< 30%The evidence contradicts it. Confidently false as stated.
A standing changes only when the score moves past a boundary by more than 4 points, the re-scoring noise floor; a score within 4 points of a boundary keeps its previous standing.
Where the evidence sits in time
Long-standingMost of this evidence is older than the rest of this field.