Lactobacillus gasseri

L. gasseri

Snapshot

Indications	Contraindications
Irritable bowel syndrome^{1, 2} Functional constipation³ Vaginal microbiota support⁴ Stress-related symptoms^{5, 6} Sleep quality⁵ Abdominal adiposity⁷ Functional constipation³ Helicobacter pylori suppression^{8, 9}	Not intended for children¹⁰ Anticipated surgery¹⁰ Milk, soy, or wheat allergy¹⁰

Lactobacillus gasseri is a lactic acid bacterium that colonizes the human gut and vagina, with strain-specific probiotic effects that act through mucosal adhesion, antimicrobial activity, and immune modulation¹¹. Supplementation is used for gut function, including abdominal pain in irritable bowel syndrome (IBS) and functional constipation^1–3. It is also used for vaginal microbiota support, for stress-related symptoms and sleep, and for abdominal adiposity.

Evidence is strain-specific and varies by use. The IBS data include an uncontrolled multicenter study that its authors say needs placebo-controlled confirmation. Weight results are split: a fermented-milk strain reduced abdominal fat⁷, while another strain produced no significant between-group weight change¹². In women recovering from bacterial vaginosis, oral strains did not improve cure rates¹³. In healthy women, a 2025 randomized trial found an orally taken strain in vaginal swabs, with no treatment outcome tested. Products are mostly capsules, and some trials use heat-inactivated cells; see Form comparison.

Case reports describe bacteremia and liver abscess from Lactobacillus gasseri, including in a patient with diabetes and prior abdominal surgery¹⁴. A high-dose trial in healthy adults identified no safety concerns¹⁵. Per product labels, those taking medication or with a medical condition are told to consult a healthcare provider first¹⁰.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

50 sources, 36 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources