It's no secret that your gut can get in the way of sex — if you've eaten a lot or are experiencing indigestion, the pain and discomfort involved can definitely with your sex life.

However, there's a major, unexpected relationship between the gut and your sexual health and libido — and it's still being investigated by scientists.

Lately, medicine has uncovered many ways in which the gut, particularly the population of bacteria living in your intestines and bowel called the gut microbiome, can affect our health and behaviour. Sex is no different; from the hormones of sexual behaviour to the actual matter of attraction, it seems that the gut has a complex role to play in getting busy.

It's well-known that sex for people who have irritable bowel syndrome and other gut health issues can be tricky or stressful; Everyday Health reported in 2018 that worries about sex can trigger IBS symptoms and that men with IBS report having erectile dysfunction more often than men without it. This is just one piece of the connection between gut health and sexual health, but there are many other elements that might be affecting your sex life.

It's important not to underestimate the power of the gut. Here are three important ways the two may be connected.

1. The gut helps produce serotonin that affects your sex life

First and foremost, your sexual health is connected to the gut because of the neurotransmitter serotonin. If you've heard of serotonin, you'll likely know about it in connection to the brain, where it has a role in your mental health. Science has begun to uncover the fact that the vast majority of serotonin is produced by gut bacteria. "It turns out that only some serotonin is produced in the brain — about 80 to 90 per cent of it is actually produced in the gut," Dr Edward Catalano told HuffPost in 2017. Serotonin isn't just about mood and depression; it also regulates bowel movements and feelings of nausea.

Importantly, serotonin levels also have a role in how much sex we have. "Generally speaking, high levels of serotonin [....] inhibit sexual behaviour. This means that antidepressants which increase serotonin cause problems like longer time to ejaculate in men," noted Scientific American in 2011. Low levels, meanwhile, can increase your libido. A gut that's producing varying levels of serotonin may be driving unexplained mood and libido changes and shifting your sexual landscape.

2. UTIs can be caused by gut bacteria

Gut health is important when it comes to the health of our intimate parts, too. One particular area where the gut microbiome affects sexual health is urinary tract infections (UTIs). "Most UTIs are caused by E. coli that live in the gut and spread to the urinary tract," explained the Washington University School Of Medicine in 2017. E.coli isn't always a bad thing; in our guts, it's usually completely harmless and healthy. However, when it manages to migrate, it spells trouble.

Many people will have UTIs in their lifetimes — between 50 and 60 per cent of people with vaginas, according to data from 2013 — and a study in 2017 found that it's not actually as simple as one transfer of bacteria from the gut to the bladder or vagina. One bacterium commonly found in the vagina, Gardnerella vaginalis, can trigger recurrent UTI issues; it causes E.coli left over from previous UTIs to grow again, causing a new infection. Current antibiotics don't actually treat Gardnerella vaginalis, which is possibly why recurrent UTIs are so difficult to treat. It's not yet known if imbalanced levels of E.coli or gut problems make UTIs more common overall.

It's not just the gut that needs balanced bacterial populations to be healthy, either. A study in 2011 found that people who took vaginal probiotics, which contain live bacteria aimed at producing healthy populations of bacteria, were less likely to develop UTIs.

3. It's possible gut microbes might make us sexy

According to research by microbiologist Susan Erdman, the microbiome of the gut may be important for a crucial ingredient in sex: attraction. She told The New York Times in 2017 that microbes in our guts can affect our skin, hair, even our oxytocin levels. She called it "the glow of health", and believes that it has a strong role in whether we're sexually attractive to others; our guts, according to this theory, play a very strong role in our appearance as attractive mates.

It's also theorized by some scientists that 'compatible' gut microbe populations play a role in healthy relationships and good attraction; if your microbial levels match mine, we're more likely to be attracted to one another. A study in 2017 found that living with a partner over time changes both your microbiomes, making them slightly more similar, but not entirely. There's a lot about this theory that still needs to be proven, but it's an interesting perspective on the many ways gut microbes — which, for many of us, feel distant, invisible or slightly gross — can have real-world implications for our behaviour.

Your gut may not be on your mind the next time you decide to slip between the sheets, but it has a greater role in your sex life than you might think — and if it's not healthy, chances are that the impacts may be felt in your bedroom.