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Lactobacillus Gasseri Benefits: What the Research Shows
Lactobacillus gasseri is a probiotic bacterial species naturally found in the human body, including the digestive tract, and has been isolated from breast milk. Specific strains have been studied mainly for reducing belly (visceral) fat, with modest results in small trials.
Last updated 6 October 2026
Lactobacillus Gasseri: the short answer
Human evidence for L. gasseri is limited and strain-specific. Small trials in Japan and Korea found that the SBT2055 and BNR17 strains modestly reduced belly (visceral) fat over 12 weeks, and the effect faded after people stopped. Single small trials suggest possible benefits for IBS, menstrual pain and sleep, but these need confirmation.
| What it is | A lactic acid bacterium that lives naturally in the human gut, mouth and vagina; some strains used in supplements were isolated from breast milk. Effects depend on the strain, such as SBT2055 (LG2055), BNR17, OLL2809 and CP2305. |
|---|---|
| Most studied for | Abdominal (visceral) fat and waist size (SBT2055, BNR17); diarrhea-predominant IBS (BNR17); menstrual pain in endometriosis (OLL2809); sleep quality under stress (CP2305); common colds (as part of a multi-strain product). |
| Amounts used in studies | SBT2055 trials gave 200 g a day of fermented milk supplying roughly 200 million to 20 billion CFU per day for 12 weeks. BNR17 trials used 1 billion or 10 billion CFU per day for 12 weeks. OLL2809 was given as one 100 mg tablet daily for 12 weeks. |
| Strength of evidence | Limited: small trials in Japan found SBT2055 cut visceral fat area by about 4.6% to 8.5% from baseline over 12 weeks, fading after stopping; a Korean BNR17 trial found less visceral fat than placebo at the higher dose. Other uses rest on single small trials. |
| Safety | Generally well tolerated in trials of about 12 weeks; mild gas or bloating can occur. Long-term data are limited. GRAS status is strain- and use-specific (for example, FDA had no questions about strain NCIMB 30370 in foods). Premature infants and severely ill or immunocompromised people face a rare risk of serious infection and should ask a doctor first. |
| In products we review | LeanBiome (Biome), FemiCore |
Sources: SBT2055 abdominal fat trial · BNR17 visceral fat trial · FDA GRAS notice 1089 letter · NCCIH probiotics safety overview
Benefits of Lactobacillus Gasseri
What is Lactobacillus Gasseri?
Lactobacillus gasseri is a species of Gram-positive, anaerobic, rod-shaped bacteria belonging to the genus Lactobacillus. It is a key member of the human microbiota, naturally colonizing the gastrointestinal tract, the urinary tract, and the vaginal canal. Unlike many probiotics sourced from fermented dairy or plants, L. gasseri naturally lives in the human body and tolerates acid and bile, but long-term colonization from supplements has not been shown.
The History and Discovery of L. Gasseri
For many years, Lactobacillus gasseri was classified as part of the Lactobacillus acidophilus group due to their similar morphological and biochemical characteristics. However, in 1980, advanced DNA-DNA hybridization techniques allowed scientists to identify it as a distinct species. It has been found in human breast milk and may be passed from mother to infant, but its specific role in infant immune and gut development is not well established. In recent decades, it has become a 'functional' ingredient, largely due to Japanese trials of the SBT2055 strain on abdominal fat.
Top Rated Supplements with Lactobacillus Gasseri
Products we review that list Lactobacillus Gasseri as an ingredient. Not every product discloses how much of each ingredient a serving contains, so check each review before assuming it matches the amounts used in studies.
LeanBiome, now sold as Biome by Lean for Good, is a capsule marketed for weight management through gut health. Its label lists nine probiotic species (20 billion CFU a day), a small amount of inulin, a caffeine-free green tea phytosome and two plant extracts, Sphaeranthus indicus and mangosteen rind. The combined formula has not been tested in a published trial, and the two plant extracts are at half the dose used in trials of a similar blend, so any effect on weight is unproven.
FemiCore is a one-a-day capsule sold to women over 45 for bladder leaks and urinary health. This review covers its full label, including bearberry, an herb meant for short-term use, what research shows for bladder leaks and urinary tract infections, the sales claims about dioxins and the “urinary microbiome”, the prices and the 60-day refund.
Scientific Analysis of Lactobacillus Gasseri
The Mechanism of Action: How L. Gasseri Works
Lactobacillus gasseri functions through several complex biological pathways. As a lactic acid-producing bacterium, its primary role is to ferment carbohydrates into lactic acid, which lowers the pH of its environment. In lab studies, this acidity can inhibit microbes such as E. coli and Candida albicans; protection against infections in people has not been established. Beyond simple pH regulation, L. gasseri is known for producing bacteriocins—natural antimicrobial peptides such as gassericin A—which specifically target and inhibit the growth of competing harmful microbes.
Perhaps the most unique mechanism of L. gasseri is its interaction with lipid metabolism. Research suggests that this strain may influence the size of fat cells (adipocytes) and interfere with the absorption of dietary fat in the small intestine. One small 7-day trial found SBT2055 increased fat excreted in stool, which may slightly reduce the fat absorbed from food. In mouse studies, SBT2055 reduced inflammation-related gene activity in visceral fat (the fat around internal organs); this has not been confirmed in people.
Health Benefits and What the Research Shows
1. Weight Management and Visceral Fat Reduction
Certain L. gasseri strains have been studied for their effects on body fat, with modest results. In a double-blind, multicenter trial in Japan, 210 adults with high visceral fat drank 200 g a day of fermented milk with or without the L. gasseri SBT2055 strain. After 12 weeks, visceral fat area fell from baseline by an average of 8.5% (higher dose) and 8.2% (lower dose), with no significant fall in the control group. Additionally, participants experienced significant decreases in body mass index (BMI), waist circumference, and hip circumference. When participants stopped drinking the fermented milk for 4 weeks, these effects weakened, suggesting continued intake may be needed to maintain them.
2. Enhancing Digestive Health and Gut Barrier Integrity
In mouse studies, L. gasseri SBT2055 reduced intestinal permeability; this has not been confirmed in people. Claims that it prevents 'leaky gut' or the inflammation linked to it in people are not supported by human studies. Small Korean trials of the BNR17 strain reported improvement in diarrhea-predominant Irritable Bowel Syndrome (IBS), but larger studies are needed. It can adhere to the intestinal lining in lab studies, which may help it compete with pathogens, but effects on the microbiome in people are uncertain.
3. Immune System Modulation
Lab and mouse studies suggest L. gasseri SBT2055 can increase production of Immunoglobulin A (IgA), an antibody that helps defend the mucous membranes. One trial in 479 adults found a product combining L. gasseri PA 16/8 with two bifidobacteria shortened colds (7.0 vs 8.9 days); evidence for L. gasseri alone is limited. Effects on Th1 and Th2 immune balance come from lab studies, and benefits for seasonal allergies or asthma have not been shown in people.
4. Vaginal and Urinary Tract Health
For women, L. gasseri is a dominant species in a healthy vaginal microbiome. It produces lactic acid that helps keep vaginal pH low, but evidence that supplements prevent Bacterial Vaginosis (BV) or yeast infections is limited. One small trial in 62 women with endometriosis found L. gasseri OLL2809 tablets reduced menstrual pain over 12 weeks compared with placebo; larger trials are needed.
Potential Side Effects and Safety Profile
In the US, GRAS status is strain- and use-specific: for example, the FDA had no questions about L. gasseri NCIMB 30370 for use in foods. The species is on the EU's QPS list. However, some users may experience mild side effects during the first few days of supplementation, including:
- Mild bloating or flatulence as the gut microbiome recalibrates.
- Temporary changes in bowel movements.
- Abdominal gurgling.
These symptoms are typically transient and subside as the body becomes accustomed to the new bacterial balance. Individuals with severely compromised immune systems, such as those undergoing chemotherapy or organ transplant recipients, should consult with a physician before starting any probiotic regimen, as there is a very rare risk of systemic infection in highly vulnerable populations.
Synergy with Other Ingredients
L. gasseri is sometimes paired with prebiotics like Inulin or Fructooligosaccharides (FOS), though benefits of this pairing are not well tested. These non-digestible fibers serve as 'food' for the bacteria, helping them thrive and colonize more effectively. Combinations with other strains like Bifidobacterium animalis are sold, but evidence that they work better for fat loss is lacking.
Frequently Asked Questions
Body-fat trials have used roughly 200 million to 20 billion Colony Forming Units (CFUs) per day, depending on the strain, usually for 12 weeks. It is important to look for a supplement that guarantees this count through the expiration date.
There is little human research on the best time to take L. gasseri; in the main SBT2055 trials it was consumed daily in fermented milk. Whether taking it at bedtime works better has not been studied.
Trials reported modest fat reductions over 12 weeks, but the effects were small and faded after stopping. It may slightly reduce fat absorption, based on one small study, but it is not a substitute for a healthy diet.
Most trials lasted about 12 weeks with few side effects; long-term safety data are limited. Many people take it daily to maintain digestive regularity and immune health.
This depends on the manufacturing process. While many high-quality probiotics are now shelf-stable due to freeze-drying technology, checking the label is essential. If the product is not shelf-stable, heat can kill the live cultures.
⚖️ Conclusion
Lactobacillus gasseri is notable for strain-specific trials on body fat, mostly small and conducted in Japan and Korea. Randomized trials of the SBT2055 strain in Japan found modest reductions in visceral fat and waist size over 12 weeks, which weakened after intake stopped. Claims about gut barrier and immune support rest mainly on lab and animal studies, and evidence that supplements improve vaginal health is limited. It is not a weight-loss solution; at most, specific strains may offer a small added effect alongside a healthy diet and exercise. Increased fat excretion in one small study offers a possible explanation, but how it works in people is not well understood. For abdominal fat, specific strains have limited but encouraging evidence; benefits for digestion or the gut-brain axis are less certain. If you choose a supplement, look for the strain name and a CFU count guaranteed through the expiration date.