Probiotics

Evidence ratingModerate

Live microorganisms that confer a benefit when taken in adequate amounts. A meta-analysis of 43 RCTs reports significant improvement in overall IBS symptoms and abdominal pain versus placebo (risk ratio 0.79). Effects are highly strain-specific, with large differences between products. Influence on immune markers such as secretory IgA is also reported in several studies.

An ingredient with growing research

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Effects reported in research

Improvement in IBS symptoms and abdominal pain reported in meta-analysis (strain-dependent)

Effects on immune markers such as increased secretory IgA reported

Dosage & timing

Generally 1–100 billion CFU/day.
Because effects are strain-specific, choose products that name the genus, species, and strain (e.g., Lactobacillus rhamnosus GG) and match your goal, with an adequate cell count.

Cautions

•Generally considered safe for healthy people, though bloating or gas can occur early on.
•People with serious illness or immune compromise should consult a doctor.
•Broad claims like 'boosts immunity' are an oversimplification.
•This site is for educational reference only.

Supporting research

Meta-analysis

Effects of probiotics on gut microbiota, IBS symptoms, and immune function: a meta-analysis

American Journal of Gastroenterology, 2014

A meta-analysis of 43 RCTs. Probiotics significantly improved global IBS symptom scores and abdominal pain compared to placebo (risk ratio 0.79). However, effects varied considerably by strain, with more consistent improvements seen in multi-strain Lactobacillus and Bifidobacterium products. Multiple studies also reported improvements in immune markers, including secretory IgA and inflammatory cytokines.

View study details

Last checked: 2026-06-25