A Pilot Study Investigating the Impact of Oral Probiotic Supplementation on the Vaginal Microbiota and Aspects of Well-being

Abstract

This double-blind, randomised, placebo-controlled pilot study investigated the effects of a six-strain probiotic formulation containing Lactobacillus crispatus CUL40 and L. gasseri CUL09 on vaginal microbiota composition and well-being in 40 women with recurrent vaginal discomfort. Participants received either the probiotic (20 billion colony-forming units/day) or placebo for 20 days. Vaginal samples collected at baseline, midpoint and endpoint were analysed using shotgun metagenomic sequencing, microbial culture and species- and strain-specific quantitative polymerase chain reaction. Vaginal symptoms and broader well-being were recorded daily. At endpoint, vaginal detection of CUL40 and CUL09 was significantly higher in the probiotic group, with neither strain detected in the placebo group. Viable L. crispatus CUL40 was recovered from vaginal cultures, whereas viable CUL09 was not recovered. L. gasseri relative abundance was significantly higher in the probiotic group at midpoint and endpoint, while Gardnerella counts were significantly lower at endpoint. Probiotic supplementation significantly influenced beta diversity over time between groups, although community state types remained broadly stable. During the second half of the intervention, rates of vaginal itchiness, burning sensation and anxiousness were significantly lower in the probiotic group. Bloating was also less frequent throughout the intervention. These findings demonstrate increased vaginal detection of orally administered probiotic strains, including recovery of viable CUL40, alongside changes in vaginal microbiota composition and reduced vaginal discomfort. Larger studies are warranted to confirm these exploratory findings and establish longer-term effects. This trial was registered at ClinicalTrials.gov (NCT07364383).