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Probiotics
Supplements · Strong evidence
Evidence
75
Impact
48
Probiotics have strong evidence for preventing antibiotic-associated diarrhea and easing IBS symptoms, with promising but strain-specific evidence for mood.
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10 studies reviewed · 10 meta-analyses
Score history
Research summary
- Probiotics have some of the more consistently positive supplement evidence for a specific, common problem: multiple meta-analyses, including a landmark JAMA meta-analysis and two Cochrane reviews (one in children, one for C. difficile-associated diarrhea specifically), find probiotics meaningfully reduce the risk of antibiotic-associated diarrhea.
- For irritable bowel syndrome, a 2023 Gastroenterology meta-analysis and several network meta-analyses find probiotics improve symptoms, including in the constipation-predominant subtype, though effects vary meaningfully by strain — a detail that plain "probiotics work" claims tend to obscure.
- Evidence for mental health via the gut-brain axis is newer and more mixed: meta-analyses find modest reductions in depressive symptoms and subclinical psychological symptoms in healthy people, with a specific strain (Lactobacillus reuteri) showing promise in a 2025 meta-analysis, but strain-specificity and study heterogeneity mean this evidence is less mature than the gut-health literature.
Gut Health
Studies10 considered · latest 2025
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