The gut–vagina connection: are your microbiomes linked?

We hear about gut health everywhere. From probiotics and prebiotic fibre to fermented foods and the latest microbiome research, there is growing awareness of how the trillions of microorganisms living in our gut can influence our health.

But another microbiome deserves equal attention: the vaginal microbiome. Surprisingly, these two microbial ecosystems may not be as separate as we once thought.

Your gut and vaginal microbiomes are connected (not literally…)

While your gut and vagina are not physically connected, there is still a relationship between these two microbial ecosystems, known as the gut-vaginal axis ^[1].

The gut and vagina each have their own distinct microbial communities, shaped by factors including hormones, immunity, diet, environment and other aspects of our biology. However, some of the microorganisms found in these two environments can overlap.

Research has identified shared bacterial species in the gut and vaginal tract, raising an interesting possibility: could the gut serve as a reservoir for bacteria capable of reaching and colonising the vagina?

The answer isn’t as simple as “yes”, but there is growing evidence that microorganisms in different parts of the body can interact and influence one another.

Where does Lactobacillus come in?

One of the most interesting examples involves Lactobacillus.

Lactobacilli are important members of many healthy vaginal microbiomes. Certain species, particularly Lactobacillus crispatus, can produce lactic acid, helping to maintain the vagina’s naturally acidic environment ^[2].

This acidity can contribute to colonisation resistance, making it more difficult for some potentially harmful microorganisms to establish themselves. Research has additionally found associations between the presence of Lactobacillus in both the rectum and vagina and a lower prevalence of bacterial vaginosis (BV) ^[3].

A possible microbial reservoir

The idea that the gastrointestinal tract could act as a reservoir for bacteria that can subsequently colonise the vaginal tract makes biological sense; microorganisms can move between nearby body sites, and the gut contains an enormous and diverse microbial community ^[4]. However, the relationship is complex as the presence of a particular bacterium in the gut does not necessarily mean that it will successfully colonise the vagina. The vaginal environment has its own ecological conditions (known as a ‘niche’) which differ from the gut’s, such as acidity level, oxygen levels, and interactions with different epithelial cell types lining the gut or vagina.

So rather than thinking of the gut as simply “donating bacteria” to the vagina, it may be more useful to think about interconnected microbial ecosystems.

Why does this matter?

Understanding the gut–vagina relationship could have important implications for how we think about vaginal health.

For conditions such as recurrent bacterial vaginosis, conventional approaches often focus on treating the vaginal environment itself (e.g. antibiotic treatment). But if microbial communities elsewhere in the body can influence which bacteria can establish in the vagina, there may be opportunities to think beyond the vagina alone.

This is an area where research is still developing. We need to better understand which microorganisms move between body sites, how they interact with existing communities, and what determines whether they support or disrupt vaginal health.

It also highlights that we may need to stop thinking about individual body sites in isolation, as the microbiome is not just a collection of separate communities. It is a network of microbial ecosystems interacting with one another - and with our bodies.

The bottom line

Your gut and vaginal microbiomes are different ecosystems, but they may be more interconnected than we once realised. As our understanding of the microbiome continues to grow, the future of vaginal health research may involve looking not only at what is happening in the vagina, but also at the wider microbial environment surrounding it.