Eating habits directly influence vaginal microbiome, research finds

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Jul 7 2025

Diet may play a key role in maintaining vaginal health by shaping microbial composition through nutrient and metabolite interactions.

Study: Dietary habits and vaginal environment: can a beneficial impact be expected? Image Credit: Kateryna Kon / Shutterstock

In a recent article published in the journal Frontiers in Cellular and Infection Microbiology, researchers in Italy investigated the role of different dietary macronutrients in influencing the composition of vaginal microbiota in women of reproductive age.

They found that women who consumed more animal protein, particularly processed and red meat, and alcohol, displayed a shift towards less healthy vaginal microbial communities, whereas those who consumed more of certain plant-derived nutrients, specifically α-linolenic acid (an omega-3 fatty acid found in nuts and seeds), showed more protective bacterial profiles. Moreover, higher intake of total carbohydrates, vegetable proteins, fiber, and starch was negatively correlated with Gardnerella spp., suggesting these nutrients may help protect against vaginal dysbiosis.

Background

In reproductive-aged women, vaginal health is largely maintained by the presence of Lactobacillus species, which help prevent infections by inhibiting the growth of harmful microbes.

When Lactobacillus levels drop and anaerobic bacteria, such as Gardnerella and Prevotella, become dominant, a condition known as bacterial vaginosis (BV) can occur. BV is marked by shifts in vaginal metabolites and is linked to higher risks of sexually transmitted infections and complications during pregnancy.

Advances in gene sequencing have allowed researchers to classify vaginal microbial communities into five community state types (CSTs).

CSTs I, II, III, and V are dominated by different Lactobacillus species, with L. crispatus, L. gasseri, and L. jensenii considered protective. CST IV, in contrast, reflects a dysbiotic state associated with BV and is largely devoid of Lactobacillus.

Although several factors such as sexual behavior, stress, and hormones are known to influence vaginal microbiota, the role of diet, especially macronutrient intake, has been understudied.

Previous findings suggest that animal protein may increase the risk of BV, while higher fiber and carbohydrate intake could be protective. This study aims to elucidate the impact of dietary patterns on the vaginal microbial and metabolic environment in young women.

About the Study

This cross-sectional study included 113 sexually active, non-pregnant women aged 19–30 from Italy. The goal was to determine associations between dietary patterns, microbiota composition, and vaginal metabolites.

Participants were excluded if they had used antibiotics in the past month, were menstruating at the time of sampling, had chronic illnesses, human immunodeficiency virus (HIV), or urogenital infections, or had ever been pregnant. Health-related, lifestyle, and demographic information, including stress levels as measured by the Perceived Stress Scale (PSS), was collected.

Each participant provided two self-collected vaginal samples during the late follicular phase. One was tested for sexually transmitted infections; the other was used for metabolomic analysis (1H-NMR spectroscopy) and microbiota profiling via 16S rRNA sequencing.

Microbial communities were classified into community state types (CSTs) using the VALENCIA tool, and Lactobacillus species were identified with high specificity using a custom reference database.

Dietary intake over the past year was assessed through a validated food frequency questionnaire with 188 food items grouped into 24 categories.

Nutritional data were processed and analyzed for alcohol, energy, and macronutrient intake, and macronutrient balances were examined using Compositional Data Analysis (CoDA), employing additive log-ratio transformations.

Statistical analyses included correlation studies, diversity indices, and multinomial logistic regression adjusted for potential confounders such as stress, contraceptive use, age, and body mass index (BMI).

Key Findings

The study analyzed the vaginal microbiota and dietary intake of 113 healthy young women with a median age of 21 years.

Microbiota samples were categorized into CSTs, with CST I, II, and V dominated by Lactobacillus crispatus, CST III by L. iners (considered a 'transitional' species with fewer protective capabilities), and CST IV by bacteria associated with vaginal dysbiosis (such as Gardnerella and Prevotella). CST IV exhibited higher microbial diversity and lower abundance of L. crispatus.

Multinomial regression revealed that a higher balance of animal proteins (especially from processed and red meats) was significantly associated with CST IV, suggesting a potential link between dysbiosis and animal protein consumption.

Alcohol intake was also positively associated with CST IV and specifically correlated with higher levels of Gardnerella and Ureaplasma. Conversely, a greater intake of α-linolenic acid (an omega-3 fatty acid from plant sources, such as nuts and seeds) was negatively associated with CST III, suggesting a healthier L. crispatus-dominated environment. Moreover, higher intake of total carbohydrates, vegetable proteins, fiber, and starch was negatively correlated with Gardnerella spp., suggesting these nutrients may help protect against vaginal dysbiosis.

Correlation networks showed distinct relationships among bacteria, nutrients, and metabolites. For example, L. crispatus was positively associated with amino acids and beneficial metabolites (e.g., 4-hydroxyphenyllactate), while CST IV bacteria correlated with simple sugars (e.g., glucose) and alcohol intake.

No significant association was found between Mediterranean diet adherence (as measured by the MEDI-LITE score) and microbiota composition.

Network representing the Spearman correlation values among bacterial, metabolite and macronutrient abundances. Bacterial taxa are depicted as red circles, metabolites as cyan squares and macronutrients as green diamonds. Edges thickness is proportional to the correlation coefficient. Only significant (p<0.05) correlations are represented. Bacteria, metabolites and macronutrients are clustered according to the indicator species analysis over the three CST groups considered.

Conclusions

This study highlights associations between dietary macronutrient intake and vaginal microbiota composition.

Higher animal protein and alcohol intake were linked with CST IV, indicative of vaginal dysbiosis, while α-linolenic acid intake favored CSTs dominated by beneficial Lactobacillus species. Additionally, carbohydrates, vegetable proteins, fiber, and starch demonstrated protective effects against dysbiosis-associated bacteria. These findings suggest diet may influence vaginal microbial balance through immune modulation, pH alteration, and bacterial translocation via the gut-vagina axis.

Strengths include comprehensive dietary assessment, detailed microbiota and metabolite profiling, and use of advanced compositional data analysis (CoDA). However, the cross-sectional design limits causal inference, and the self-selected, highly educated young cohort reduces the generalizability of the findings. Residual confounding (e.g., physical activity, sexual behavior) may also exist.

Overall, this is the first study to explore the influence of nutrient balances on vaginal microbiota using CoDA methods.

Results support the concept of a gut-vagina axis and suggest that reducing animal protein and alcohol consumption, while increasing omega-3 intake and incorporating more carbohydrates, vegetable proteins, fiber, and starch, may promote vaginal health. Future longitudinal and experimental studies are needed to confirm causality and underlying mechanisms.