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How to beneficially modulate vaginal microbiota to optimise women’s health

Each woman has a unique vaginal microbiota composition, which is dynamic and affected by diet, lifestyle, hormones, genetics, and age. In the past decade, exploration of the human microbiota has focused increasingly on vaginal microbiota composition and diversity and its impact on health, reproduction, and disease.

The vaginal microbiota plays a pivotal role in interacting with the innate vaginal immune system and in the inhibition of bacterial, fungal, and viral infections. In many healthy women, vaginal microbiota is highly populated by a few species of lactobacilli, which is extraordinary compared to other mammals.

As a key feature, vaginal lactobacilli produce lactic acid, which creates an acidic microenvironment and thus prevents the growth of potentially harmful bacteria. Sometimes the optimal bacterial composition is disrupted to an imbalanced state e.g. via antibiotic use or lifestyle changes. Bacterial imbalance referred to as dysbiosis is known to increase the risk for candidiasis (yeast infection) and bacterial vaginosis (BV). BV is in turn associated with urinary tract infections, increased risk of infertility, fallopian tube (uterine tube) inflammation, adverse pregnancy outcomes and preterm birth.

Moreover, dysbiosis in the vaginal tract is associated with sexually transmitted infections such as HIV, human papillomaviruses (HPV), herpes, chlamydia, and gonorrhoea.

How to beneficially modulate vaginal microbiota to improve health?

Vaginal dysbiosis and associated infections affect all women during their lifetime by causing discomfort and are the most common reasons why women seek medical care. Antibiotics are the standard treatment for BV and antifungal medicines for candidiasis.

Unfortunately, bacteria and fungi associated with vaginal infections can resist these treatments by forming biofilms, or they may have naturally acquired resistance. Furthermore, antibiotics may kill endogenous lactobacilli rapidly creating a vicious cycle of recurrent BV or candidiasis. Rigorous research has been conducted to find more effective solutions for balancing vaginal microbiota. 

The benefits of lactobacilli for vaginal health have been recognized for almost 100 years. Natural yoghurt rich in lactobacilli has been used as a traditional home-based remedy to rebalance vaginal microbiota and counteract vaginal dysbiosis. Currently, well-characterised probiotic bacteria, such as combination of Lactobacillus rhamnosus HN001 and Lactobacillus acidophilus La-14, can be used for maintaining healthy vaginal microbiota or restoring normal microbiota after antibiotic treatment. 

Probiotics may elicit beneficial effects in several ways. Since many of them are lactobacilli, their ability to produce lactic acid and lower the vaginal pH is critical. Also, probiotics may produce antimicrobial compounds and stimulate the immune system in a strain-specific manner to help to maintain balance in the vaginal tract. By adhering to vaginal epithelia, they may exclude attachment of pathogenic bacteria and compete for nutrients. 

Probiotics are available as dietary supplements or vaginal capsules and based on the recent research results, route of administration may be essential to elicit health benefits. In vaginal applications, probiotics may locally inhibit pathogen growth, whereas orally consumed probiotics first passage through the gastrointestinal tract, where they already begin providing beneficial effects by balancing gut microbiota and stimulate the immune system. 

Immuno-stimulation through the gut may ameliorate systemic inflammation and balance vaginal microbiota via so-called “gut-vagina axis”. For instance, research suggests that systemic inflammation associated with gut dysbiosis in obese women can lead to problems in reproduction such as lower conception rate, infertility, or early pregnancy loss: which is all linked to vaginal dysbiosis. However, more research is needed to identify the most optimal probiotics for vaginal health and the mechanisms of actions.

What are the future trends in vaginal microbiota research?

Advancements in molecular genomic technologies and bioinformatics tools have enabled us to dive deeper within the vaginal ecosystem and expand our understanding of its complexity. 

Current research reveals that not all non-lactobacillus dominated vaginal microbiota communities are direct implications of a disease and not all vaginal lactobacilli are necessarily optimal for health. For example, Lactobacillus iners, one of the most common Lactobacillus species dominating the vaginal tract, is frequently detected from healthy women as well as in women with BV and with prevalent HPV infections. 

In recent years, eyes have also turned to viral and fungal communities in the vaginal tract. Although vaginal bacteria outnumber viruses and fungi, they are important residents of the vaginal ecosystem. For instance, Candida albicans is one of the most abundant fungi in a healthy vaginal tract and also the leading pathogen in vulvovaginal candidiasis. Current research indicates that vaginal bacteria may not be the most optimal candidates to prevent candida. Perhaps fungi could be more potent in the fight against fungi. 

Interestingly, a certain probiotic yeast has shown to restrict Candida albicans. Future studies may also reveal novel beneficial fungal candidates that keep the fungal overgrowth in line. While continuing our efforts to investigate the dynamics of vaginal microbiota composition and the interactions with the host, we may find new therapies to promote and re-establish healthy vaginal microbiota. 

Vaginal microbiota transplantation may well be the next frontier of therapy for BV. First attempts to treat women suffering from symptomatic, intractable, and recurrent BV with vaginal microbial transplant form healthy women have already shown hope to be a serious option to counteract vaginal dysbiosis and associated infections.

Vaginal microbiota plays a crucial role in women’s health and successful reproduction. However, we are just on the verge of discovering the full potential and features of this unique microbial community within women. By utilizing all advanced technologies, exciting times lie ahead in vaginal microbiota research and we need to continue this momentum for finding new innovative and personalized solutions for improving the lives of women and future generations. 

Dr Liisa Lehtoranta is an R&D Manager at DuPont Nutrition & Biosciences, where she and the research team explore the health effects of HOWARU® probiotics, prebiotics, and other functional ingredients in preclinical and clinical settings.

The 7thMicrobiome and Probiotics R&D and Business Collaboration Forum will include a track on Women’s Health and on Early Life and Infant Microbiome. Click here to register for the conference.

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