Lactobacillus crispatus

What is Lactobacillus crispatus?

Lactobacillus crispatus is a lactic acid bacterium that is one of the most common dominant species in the healthy vaginal microbiome. Researchers often describe a crispatus-dominated vaginal community as the most stable type, and it is the species most associated with protection against bacterial vaginosis in observational research.

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

The most cited human research uses one specific strain, L. crispatus CTV-05, delivered as a vaginal suppository called Lactin-V. In a 2011 phase 2 trial of 100 premenopausal women with recurrent UTIs, recurrence occurred in 15% of the Lactin-V group versus 27% of the placebo group. The difference was not statistically significant, though women who were heavily colonized with the strain had a much lower risk. A larger 2020 trial in the New England Journal of Medicine found that vaginal Lactin-V, given after standard antibiotic treatment, reduced the recurrence of bacterial vaginosis at 12 weeks compared with placebo. An oral combination of L. gasseri and L. crispatus strains given alongside metronidazole did not improve BV cure rates in a 2023 trial, although it did shift some microbiome measures.

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

Oral L. crispatus products are common, but whether swallowed bacteria reach and colonize the vagina or bladder in meaningful numbers is not well established. The strain in FemiCore, LCr86, is not the strain used in the Lactin-V trials, and we did not find published clinical trials of LCr86 for urinary outcomes.

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.