Research synthesisLow evidenceMixed effect size4 studies · 3 beneficial · 1 neutral · 0 harmful
Across 4 studies, 3 reported beneficial effects of Lactobacillus plantarum 299v on reducing abdominal pain in IBS patients, with effect sizes ranging from moderate to large. One neutral study (n=190) found no significant difference, but the overall evidence leans toward a beneficial effect. Most studies did not specify a dose, but one used 1×10^10 CFU/day; the median study duration was 28 days, though only one study reported this.
- Effective dose range: 1×10^10 CFU/day (from one study; no clear convergence across others)
- Studied populations: irritable bowel syndrome (IBS) patients
Caveats: Evidence base is small (only 4 studies) — conclusions should be considered preliminary. The single neutral study had a larger sample size (n=190) than the beneficial studies (n=20 and n=221), which may temper the overall effect estimate. Many studies did not report duration or dose, limiting comparability. Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed).
Generated Jun 17, 2026