We’ve all heard of the gut-brain axis, but there’s also an important gut-hormone connection you should know about…    

‘Hormonal balance’ and ‘gut health’ are two buzz phrases that have certainly been hitting the headlines in recent years. It seems that every other day, another wellness influencer or brand is promoting another way to better ‘balance’ hormones or improve the state of out gut microbiome. 

Interestingly, however, the connection between the gut and hormones hasn’t been as loudly shouted about – despite an emerging body of research showing that the two areas of health are inextricably linked. 

So, what’s the connection and what does it mean for those of us trying to work towards better gut or hormonal health?

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How are our hormones and gut bacteria linked?

Our hormones are clever chemical messengers that have an important role to play in lots of our bodily functions, including digestion. It’s the role of specific hormones to tell us when we’re hungry (ghrelin) and when we’re full (leptin), but even those not obviously associated with digestion have a key relationship with our gut.

Loads of hormones are made in the gut

Some vital hormones are actually produced by the bacteria present in our gut, explains registered nutritionist Rhiannon Lambert, author of The Science of Nutrition.

“For example, did you know that 95% of serotonin (AKA our happy hormone) is produced there?”  Lambert says. “Serotonin is also involved in the conversion of melatonin (our sleep hormone) and helps regulate our circadian rhythms. There is evidence that suggests our gut microbiome is involved in the regulation of oestrogen too, one of the main female sex hormones.”  

Some vital hormones are actually produced by the bacteria present in our gut.

And let’s not forget that the gut also has a key role to play in absorbing nutrients from our food and supporting the elimination of toxins. If your natural detox system goes off-piste, that can cause hormonal imbalances. On top of this, our GI tract also houses around 70-80% of our immune system and if this becomes disrupted, it can cause issues with our hormone levels.

Suboptimal gut health = disrupted hormone production

If you’re thinking this all sounds incredibly interconnected, that’s because it is. Put simply, it means that if your gut isn’t working as effectively as it should, hormone production can be impacted – which has a knock-on effect on your mental and physical health.

Of course, it works the other way, too. High or low levels of certain hormones can impact the way our digestion works, leading to problems such as bloating, constipation, nausea or diarrhoea. You may have felt sick when stressed, or know only too well how fluctuations in our sex hormones can affect your bowel habits (yes, period poo really is a thing!). 

Which hormones are most affected by the gut?

We’ve talked briefly about how serotonin and melatonin are impacted by gut health, but many more key hormones are also connected to the gut…

Female sex hormones

Research shows there are microbes working in our gut that can tweak the amount of oestrogen in our bodies. “This part of our microbiome is called the estrobolome and it’s a collection of bacteria in the gut capable of breaking down and changing the levels of circulating oestrogen in the body,” explains Dr Federica Amati, a medical scientist and nutritionist at Imperial College London and personalised nutrition company ZOE.

On the other side, oestrogen and progesterone levels can also have a direct impact on our digestive system in terms of gut motility (how quickly food moves through our digestive system) and the composition of our microbiome. 

“High progesterone is associated with a slowing of gut movement,” says Dr Amati. “This is very useful in pregnancy when progesterone levels are high, as it gives our body more time to extract as many nutrients as possible from our food in order to help progress the pregnancy. But this can also cause constipation, so drinking plenty of water and eating fibre is very important during pregnancy and towards the second half of our menstrual cycle, when this hormone is also heightened.”  

Stress hormones

“High levels of cortisol and adrenalin have two main effects on our gut,” explains Dr Amati. “First, they drive us to prefer easy-to-absorb carbohydrates that require little effort to absorb for maximum energy. Second, they divert blood flow from our gut to our limbs, prioritising our ability to run away from the threat over the process of digesting a big meal.”

That might sound pointless in an age of laptops and concrete, but it was an absolutely vital mechanism back in the day when we used to face imminent threats. “It’s less useful if we are in a state of chronic high stress due to perceived dangers such as being late for a deadline,” Dr Amati says.

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In fact, increased stress hormones have been linked to many digestive problems. Research suggests it can change the make-up of your microbiome, resulting in an increase in harmful bacteria. It can also affect gut motility and permeability (the ability of the gut lining to act as a barrier and stop bacteria and toxins from leaking into the bloodstream).

It’s no wonder, then, that high levels of stress hormones have been linked to conditions such as irritable bowel syndrome (IBS) and inflammatory bowel disease.

Interestingly, however, a healthy gut can have a beneficial impact on these hormones. If our gut is functioning properly, it can help to regulate our stress response and reduce anxiety.

Why women need to care about the gut-hormone axis

Recent research has shown there are key differences between male and female gut microbiomes, and it’s even been given a name – the microgenderdome. For example, studies have shown that irritable bowel syndrome and autoimmune diseases are much more common in women, and data indicates that our guts can show sex-specific responses to exactly the same diet. The main reason for that? The different hormone levels between the two sexes.


“If you’re in the habit of tracking your gut health, you might have noticed that your period coincides with symptoms like loose stools, tummy pain and bloating,” says Laura Tilt, a registered dietitian and ambassador for probiotic supplement brand Symprove. 

“In one study of healthy women, 73% reported at least one gut symptom just before or during their period, most often abdominal pain and diarrhoea. The trigger for these symptoms is believed to be the drop in ovarian hormones which takes place just before your period. At the same time, there’s a spike in prostaglandin hormones which cause the uterus to contract, and which causes the gut to contract too.”

Hormonal shifts in our body caused by other events such as pregnancy can also impact our digestive system. 

At key hormonal parts of your life, your gut-hormone axis is going to change.


“Gut health can be massively impacted by the changes in our body that happen during pregnancy,” says Lambert. “For example, as your baby grows, digestion slows down and the chance of constipation increases as a result. 

“During pregnancy there are also huge fluctuations in hormone levels. These changes, especially the increase in human chorionic gonadotropin (HCG) in early pregnancy, can cause nausea. This may lead to lack of appetite and therefore less diversity in the diet, which we know is associated with poorer gut health.”


There’s the menopause to think about, too. Changes to levels of oestrogen and progesterone in the body at this time may cause slower digestion, which could lead to bloating or constipation.

How to support gut and hormonal health

It’s important to remember that our hormones and gut are part of a much bigger system and are impacted by many things in our body (as well as each other). However, science shows they are key parts of the puzzle – so how can we help our guts and hormones work in synergy and stay balanced? 

Balanced diet and good sleep

“While there is still much research to be done looking at the direct link between our guts and hormones, making sure we have a balanced and varied diet is important for many aspects of our health, including our gut and hormone health,” says Lambert. 

“It’s also important to make sure we’re getting good-quality sleep and managing our stress levels as this can have an impact on how our gut functions and our hormone levels.”

Living more intuitively 

Dr Amati adds that understanding and living in tune with how your body works can support your wellbeing.

“Responding to our body’s hunger, tiredness and social signals and getting to know how we respond to food and hormonal changes is the first step in being able to live more intuitively,” she says. 

“Working closely with women through major shifts in fertility, pregnancy and the menopause, I can see there is huge power in knowing how your body responds to fluctuations in our hormones and learning to harness your own existing biological power to maximise health, wellbeing and energy.” 

Amen to that.  

Images: Getty

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