The educational content in this post, elaborated in collaboration with Lesaffre, was independently developed and approved by the GMFH publishing team and editorial board.

Why is vaginal microbiota important for health?

While you’re familiar with the relevance of your gut microbiota for health and wellbeing, microorganisms actually exist in every area of the body that’s exposed to the outside. Your skin, ears, nose and respiratory tract all have a microbiota and so does the vagina.

The vaginal microbiota consists of a wide number of bacteria (mainly Lactobacillus species) and a small number of fungi (mostly Candida albicans). It’s important to note that, contrary to the gut microbiota, the vaginal microbiota is in good shape when its diversity is low. Simply put, lactobacilli are the predominant bacteria in the vagina, explaining the low diversity of the vaginal microbiota in healthy women. In contrast, when other bacteria (Gardnerella vaginalis, Atopobium vaginae and others) or fungi (Candida species) overgrow and lactobacilli decrease, vaginal infections can appear.

The role of the vaginal microbiota for health consists of preventing pathogenic microorganisms from establishing themselves in the vagina by:

  • Producing defensive compounds, such as lactic acid and antimicrobial substances;
  • Acting as a barrier and stimulating mucus production by the vaginal epithelium; and
  • Supporting the woman’s immune system.


Potentially harmful microbes from your gut can travel into the vagina

Rectum to vagina translocation of bacteria is one of the several known causes for vaginal dysbiosis. In other words, what happens in the gut doesn’t stay in the gut and can have an impact on your vaginal health. That is because the gut harbors a stable community of potentially harmful bacteria that can travel into your vaginal microbiota.

Our gut is the home to microorganisms that are expected to be found as members of a healthy gut microbiota but when travel to the vagina may cause problems. This is the case of some bacteria such as Escherichia coli and some fungi such as Candida species. When these microorganisms, which are normal in the rectum, move to and grow in the vagina then an imbalance of the vaginal microbiota can occur leading to a vaginal infection. It is also common that those potentially harmful microorganisms not only colonize the vagina and cause symptoms, but can also cause harm if they reach the bladder, leading to an increased risk of urinary tract infections.

The idea that the rectal microbiota is a source of microorganisms for the vagina is also supported by the observation that the vaginal and rectal microbiota are similar in terms of composition and Lactobacillus species. Furthermore, some studies supports the idea that oral administration of probiotic bacteria and yeast allows the migration of probiotic microorganisms from intestine to vagina where they may exert their benefits for vaginal health. That suggests that if your gut microbiota is in good shape, then your vagina microbiota will likely be in a protective state as well.

Another less widely studied way in which the gut microbiota affects your vaginal health is by changing levels of hormones such as estrogens that can have an impact on the vaginal microbiota.

The gut microbiota can metabolize estrogen hormones, leading to the accumulation of them within the body instead of being eliminated through feces. An increase in the estrogens in the vagina promotes the production of glycogen as a food source for beneficial lactobacilli. However, glycogen is also a nutrient for the pathogenic yeast Candida albicans, thus increasing the risk of vulvovaginal candidiasis, especially in situations such as pregnancy that favor high estrogen levels.


What are the downsides of an unbalanced vaginal microbiota?

There is no unique vaginal microbiota as it varies for every woman, depending on the phase of the menstrual cycle. Vaginal microorganisms are also affected by diet, hygiene practices, drugs, stress and illness.

When the composition of the vaginal microbiota is altered, lactobacilli are no longer the predominant bacteria in the vagina. The overgrowth of pathogenic microorganisms in the vagina can be asymptomatic in half of women or may lead to an unusual vaginal discharge that smells fishy or is thick and white and which is sometimes accompanied by soreness or itching.

An altered vaginal microbiota, or vaginal dysbiosis, has been associated with bacterial vaginosis, thrush, recurrent urinary tract infections and even reduced fertility. The findings open up the possibility of modifying the vaginal microbiota directly or indirectly by acting on the gut microbiota to improve women’s health.


Take-home messages

  • The vaginal microbiota is important for women’s health and is balanced when its diversity is low.
  • Pathogens from the gut can travel into the vagina and contribute to vaginal dysbiosis, which suggests taking care of the gut will likely improve vaginal health.
  • When vaginal lactobacilli lose their predominance, there is an increased chance of developing bacterial vaginosis, candidiasis or recurrent urinary tract infections due to colonization by pathogenic bacteria.



Bradford LL, Ravel J. The vaginal mycobiome: A contemporary perspective on fungi in women’s health and diseases. Virulence. 2017; 8(3):342-351. doi: 10.1080/21505594.2016.1237332.

Nair Balakrishnan S, Yamang H, Lorenz MC, et al. Role of vaginal mucosa, host immunity and microbiota in vulvovaginal candidiasis. Pathogens. 2022; 11(6):618. doi: 10.3390/pathogens11060618.

Marrazzo JM, Fiedler TL, Srinivasan S, et al. Extravaginal reservoirs of vaginal bacteria as risk factors for incident bacterial vaginosis. J Infect Dis. 2012; 205(10):1580-1588. doi: 10.1093/infdis/jis242.

Chen SL, Wu M, Henderson JP, et al. Genomic diversity and fitness of E. coli strains recovered from the intestinal and urinary tracts of women with recurrent urinary tract infection. Sci Transl Med. 2013; 5(184):184ra60. doi: 10.1126/scitranslmed.3005497.

El Aila NA, Tency I, Claeys G, et al. Identification and genotyping of bacteria from paired vaginal and rectal samples from pregnant women indicates similarity between vaginal and rectal microflora. BMC Infect Dis. 2009; 9:167. doi: 10.1186/1471-2334-9-167.

Decherf A, Dehay E, Boyer M, et al. Recovery of Saccharomyces cerevisiae CNCM I-3856 in vaginal samples of healthy women after oral administration. Nutrients. 2020; 12(8):2211. doi: 10.3390/nu12082211.

Yefet E, Colodner R, Strauss M, et al. A randomized controlled open label crossover trial to study vaginal colonization of orally administered Lactobacillus reuteri RC-14 and rhamnosus GR-1 in pregnant women at high risk for preterm labor. Nutrients. 2020; 12(4):1141. doi: 10.3390/nu12041141.

Antonio MAD, Rabe LK, Hillier SL. Colonization of the rectum by Lactobacillus species and decreased risk of bacterial vaginosis. J Infect Dis. 2005; 192(3):394-398. doi: 10.1086/430926.

Graham ME, Herbert WG, Song SD, et al. Gut and vaginal microbiomes on steroids: implications for women’s health. Trends Endocrinol Metab. 2021; 32(8):554-565. doi: 10.1016/j.tem.2021.04.014.

Amabebe E, Anumba DOC. The vaginal microenvironment: the physiologic role of Lactobacilli. Front Med. 2018; 5:181. doi: 10.3389/fmed.2018.00181.

Oerlemans E, Ahannach S, Wittouck S, et al. Impacts of menstruation, community type, and an oral yeast probiotic on the vaginal microbiome. mSphere. 2022; 7(5):e0023922.

Bacterial vaginosis. National Health System, 2022. Available:

Greenbaum S, Greenbaum G, Moran-Gilad J, et al. Ecological dynamics of the vaginal microbiome in relation to health and disease. Am J Obstet Gynecol. 2019; 220(4):324-335. doi: 10.1016/j.ajog.2018.11.1089.

Talapko J, Juzbasic M, Matijevic T, et al. Candida albicans – The virulence factors and clinical manifestations of infection. J Fungi (Basel). 2021; 7(2):79. doi: 10.3390/jof7020079.

Salazar AM, Neugent ML, De Nisco NJ, et al. Gut-bladder axis enters the stage: Implication for recurrent urinary tract infections. Cell Host Microbe. 2022; 30(8):1066-1069. doi: 10.1016/j.chom.2022.07.008.

Younes JA, Lievens E, Hummelen R, et al. Women and their microbes: the unexpected friendship. Trends Microbiol. 2018; 26(1):16-32. doi: 10.1016/j.tim.2017.07.008.