What is Lactobacillus gasseri?
Lactobacillus gasseri is a lactic acid bacterium found naturally in the human gut, mouth and vagina. Along with L. crispatus, L. jensenii and L. iners, it is one of the species that commonly dominates the healthy vaginal microbiome.
Like other lactobacilli, it produces lactic acid, which helps keep the vaginal environment mildly acidic. A healthy vaginal microbiome in women of reproductive age is usually dominated by one or a few Lactobacillus species, and loss of that dominance is linked to bacterial vaginosis and, in some studies, to a higher risk of urinary tract infections. That background is why lactobacilli appear in so many women’s wellness formulas.
What the research says
Research on oral L. gasseri for women’s health is early. In a 2023 randomized trial in 67 women with bacterial vaginosis, oral L. gasseri TM13 combined with L. crispatus LG55, given alongside metronidazole, did not improve cure rates compared with metronidazole alone, although the authors reported some changes in microbiome measures. Separately, specific L. gasseri strains have been studied in Japan for body weight and abdominal fat, with modest results that do not apply to other strains.
For urinary health in general, the evidence for probiotics is weaker than marketing suggests. A 2015 Cochrane review of nine trials found no significant reduction in recurrent symptomatic UTIs with probiotics compared with placebo, and noted that most studies were small with a high risk of bias. For bacterial vaginosis, a 2022 meta-analysis of randomized trials found that adding probiotics to antibiotic treatment modestly improved cure rates, but the products, strains and routes (oral versus vaginal) varied widely.
A key point, emphasized by the NCCIH and by a large 2018 systematic review of strain specificity, is that results from one strain cannot be assumed to apply to another strain of the same species. A study of one commercial strain says little about a different strain with a different code on the label.
How it’s used in supplements
FemiCore uses strain LG08 and does not disclose its amount or CFU. We did not find published trials of this strain for bladder control or urinary health.
Probiotic doses are measured in colony forming units (CFU), typically ranging from about 1 billion to tens of billions per day in research. A label that lists strains only in milligrams, especially inside a combined blend, does not tell you how many live organisms you are getting or whether they survive to the end of shelf life. Look for products that state CFU at expiration, name the exact strain, and ideally cite trials of that strain.
Probiotics are generally well tolerated in healthy people. Mild gas or bloating in the first days is common. People who are seriously ill or have weakened immune systems face a small risk of serious infection and should talk to a doctor before using them.
Safety and cautions
Generally well tolerated; mild gas or bloating can occur at first. People with weakened immune systems, serious illness, central venous catheters or recent surgery should talk to a doctor first because of a small risk of serious infection. Product quality varies and some probiotic products have been found to contain organisms not listed on the label. Do not use a probiotic in place of medical care for a suspected infection.
Supplements we reviewed that contain it
★★★☆☆
FemiCore reviewFemiCore is a once-daily capsule combining cranberry, bearberry, berberine, mimosa pudica and five lactobacillus strains, marketed for bladd...
