Lactobacillus gasseri
EVIDENCE: WEAKAlso sold as: L. gasseri, LG08, L. gasseri CECT 30648, SBT2055
L. gasseri is common in healthy vaginal bacterial communities, and some oral preparations have shown vaginal colonization. Direct urinary benefits remain unestablished, so colonization findings should not be treated as proof of bladder effects.
Compiled by iSupplementReviews editorial team ·Updated 2026-10-10 · 3 sources
- Type
- Probiotic — vaginal microbiome species
- Studied dose
- 10⁹ CFU/day orally (colonization trial); vaginal-suppository studies used similar orders
- Best form
- Named strain with demonstrated vaginal colonization (e.g., CECT 30648) — most gasseri strains are uncharacterized
- Our rating
- WEAK — Mostly small, animal, or traditional evidence
What is Lactobacillus gasseri?
L. gasseri occurs in the gut and is one of the species common in healthy vaginal communities. Specific oral preparations have shown vaginal colonization. That finding supports one step in the proposed mechanism, rather than proving a urinary benefit.
Other names and forms it’s sold as
- CECT 30648: the colonization-validated vaginal strain
- SBT2055: the weight-management strain in Japanese trials
- LG08 and similar IDs: commercial strains with no published human data
- Mostly appears in multi-strain vaginal-health blends
Where does it come from?
Human commensal: gut, vagina, breast milk. Supplement strains are industrial isolates.
How does it work in the body?
Classic vaginal-lactobacillus mechanisms: lactic acid production maintaining protective low pH, hydrogen-peroxide and bacteriocin output, competitive exclusion of Gardnerella, Candida, and E. coli. In lab work it’s shown broad activity against urogenital pathogens; the ecological case for its vaginal role is solid.
What is it claimed to do?
Vaginal flora balance (well-grounded), weight management (real strain-specific trials), urinary protection (extrapolation), and bladder control (no evidence).
What does the research show?
| Claim | Evidence | Dose studied | Verdict |
|---|---|---|---|
| Colonizes vagina after oral dose | 2025 RCT — strain-specific | 10⁹ CFU/day ×18 days | Demonstrated (CECT 30648) |
| Shifts vaginal community toward lactobacilli | Same trial | 10⁹ CFU/day | Early positive |
| UTI / bladder outcomes | None | — | Unproven |
| Visceral fat (SBT2055) | Japanese trials | ~10⁸–10⁹ CFU | Separate strain, separate claim |
The colonization finding — why this species is interesting
One trial detected a specific orally taken L. gasseri strain in vaginal samples in some participants. Detection and changes in bacterial communities do not establish a urinary-health benefit.
The 2025 Microbiology Spectrum trial: 48 healthy women took oral L. gasseri CECT 30648 (10⁹ CFU, alone or with L. crispatus) for 18 days. The strain was detectable in vaginal swabs of ~56% of treated participants, confirmed by strain-specific PCR, and vaginal communities shifted toward lactobacilli-dominated states. It’s the rare experiment that closes the oral-to-vaginal loop rather than asserting it.
Two caveats: the colonization was demonstrated for this strain (CECT 30648), not for gasseri generally; and “reaches the vagina” is still not “reaches the bladder” or “reduces leaks.”
The urinary link — ecological, not clinical
Vaginal lactobacilli quantity correlates with urinary lactobacilli (the 2023 qPCR study) and inversely with UTI risk, so restoring vaginal flora is a plausible indirect route to urinary benefit. But every link after “colonizes the vagina” remains unproven for this species.
What doesn’t L. gasseri do?
No trial shows it reducing UTI incidence, urgency, frequency, or leakage. Its vaginal-colonization data is meaningful for BV-style outcomes, and silent on bladder ones.
What dose was studied?
| Goal | Dose | Form/route | Duration |
|---|---|---|---|
| Vaginal colonization | 10⁹ CFU/day | oral capsule | 18 days |
| Weight management (SBT2055) | ~10⁸–10⁹ CFU/day | oral, fermented milk | 12 weeks |
Side effects
Clean safety record in trials; the 2025 colonization study reported good tolerability. Standard probiotic cautions for the severely immunocompromised.
Drug interactions
- Antibiotics: space or post-course dosing
- Immunosuppressants: class-level caution
Who should not take it?
Severely immunocompromised patients; everyone else has clean data.
What the authorities say
General probiotic frameworks apply: NCCIH (safe in healthy people) and ISAPP strain-specificity. No regulator has evaluated gasseri for urinary indications; its institutional footing is as a food-grade organism with emerging clinical research.
What to know about Lactobacillus gasseri
Oral-to-vaginal findings for specific L. gasseri preparations do not establish bladder benefits. Direct urinary evidence remains missing. Keep the strain, route, and measured outcome separate when reading a supplement claim.
Frequently asked questions about Lactobacillus gasseri
Can oral L. gasseri reach the vagina?
Yes, unusually, it's been demonstrated: a 2025 randomized trial found oral L. gasseri CECT 30648 (10⁹ CFU/day for 18 days) detectable in vaginal swabs of ~56% of women on active treatment versus placebo. That's strain-specific evidence for the oral-to-vaginal route most probiotic claims merely assume.
Does L. gasseri help with UTIs or bladder control?
No direct evidence. The rationale is ecological: L. gasseri is a core member of healthy vaginal flora, and vaginal lactobacilli status correlates with UTI risk. But no trial has tested gasseri for UTI, urgency, or leaks.
What else is L. gasseri known for?
Weight-management research, oddly; the SBT2055 strain has Japanese trials on visceral fat. It's also a common vaginal community member and has documented laboratory activity against Candida and bacterial-vaginosis organisms.
How is L. gasseri different from L. crispatus?
Both are core vaginal species, but crispatus dominates the most protective community type and has the direct UTI-prevention trial (vaginal route). Gasseri's distinguishing evidence is the demonstrated oral-to-vaginal colonization. Different species, different proof points.
References
Products we reviewed containing Lactobacillus gasseri
Based on recorded labels or seller-described formulas. Inclusion does not establish a match to the strains, preparations or amounts studied here; check each review's disclosure limits.