Daily Vaginal Microbiota Fluctuations Associated with Natural Hormonal Cycle, Contraceptives, Diet, and Exercise Original paper

What was studied?

This research investigated how the vaginal microbiota of healthy young women fluctuates daily in association with the natural hormonal cycle, contraceptive use, diet, and exercise. The authors used daily self-collected vaginal swabs over a period of 10 weeks to assess microbial community dynamics with high temporal resolution through 16S rRNA gene sequencing. The study sought to understand the role of endogenous estradiol, exogenous hormonal contraceptives, and lifestyle factors in regulating vaginal microbial diversity, Lactobacillus dominance, and community stability.

Who was studied?

The participants included 26 healthy female college students aged 18 to 22 years from Wellesley College. They submitted daily vaginal swabs while recording information about their menstrual cycle, contraceptive use, dietary habits, exercise routines, and mood (collected during the second year). The cohort was categorized based on contraceptive use into women not using hormonal contraceptives, those using combined estrogen-progestin systemic contraceptives, and those using locally released progestin-only contraceptives. This diverse grouping allowed comparison of how different hormonal exposures and lifestyle factors influence the vaginal microbiome.

Most important findings

The vaginal microbial communities clustered into five distinct community state types dominated by different Lactobacillus species or more diverse anaerobic bacteria. During menstruation, microbial diversity increased significantly while Lactobacillus abundance decreased, indicating a disruption in the typically protective Lactobacillus dominance linked to menstrual bleeding and hormonal fluctuations. The study revealed a strong correlation between estradiol levels and vaginal microbial diversity and stability in naturally cycling women and those on combined contraceptives, but this relationship was disrupted in users of local progestin-only contraceptives. Women using local progestin-only contraceptives exhibited altered microbial fluctuations and lower Lactobacillus levels, suggesting that hormonal composition and release method affect microbiome structure. Additionally, a vegetarian diet and increased exercise were associated with greater microbial diversity, highlighting lifestyle as a modulator of vaginal microbiota. Mood did not show significant associations, though the data were limited. These results emphasize the dynamic nature of the vaginal microbiome, shaped by hormonal and environmental factors.

Key implications

The findings of this study suggest that ovarian hormones, particularly estradiol, play a critical role in maintaining vaginal microbial stability and Lactobacillus dominance, which are important for reproductive health. Hormonal contraceptives influence these dynamics in complex ways depending on hormone type and delivery method, with local progestin-only contraceptives potentially disrupting beneficial microbial communities. Lifestyle factors such as diet and exercise also contribute to shaping the vaginal microbiome. This highlights the importance of considering both endogenous and exogenous hormonal influences alongside lifestyle factors when evaluating vaginal health. The study also underscores the value of high-frequency longitudinal sampling to capture rapid microbial changes, which could inform future interventions for preventing vaginal microbial dysbiosis and associated reproductive complications.