From menstruation to menopause – how hormones impact your gut

As scientists have become more interested in the workings of the gut and its thriving ecosystem, research has revealed several sex-specific differences in gut health and the gut microbiome. For example, irritable bowel syndrome (IBS) affects twice as many women as men (Meleine & Matricon, 2014), and women and men’s microbiota respond differently to eating the same diet (Bolnick et al., 2014).

One explanation for these differences is the impact of female sex hormones like oestrogen, which can alter digestion, gut function, and even gut microbes. Since sex hormones fluctuate throughout our life cycle (think periods, pregnancy, and menopause) so too can digestion and gut health. So, let’s take a closer look.

Cyclical gut symptoms during the menstrual cycle are common, both in healthy, usually non-symptomatic women and women with gut conditions like IBS and inflammatory bowel disease (IBD) (Bharadwaj et al., 2015). Results from one 2014 study showed that over two thirds of women experienced at least one gut symptom (most often abdominal pain and diarrhoea) close to or during their period(M.T. et al., 2014).

If we consider how sex hormones go up and down at peak points in the menstrual cycle (remembering that there are receptors lining the gut which sense and react to these hormones.), these cyclical symptoms start to make sense.

During the first part of the menstrual cycle (known as the follicular phase), oestrogen and progesterone levels rise in preparation for a possible pregnancy, and this can alter gut motility (movement), leading to constipation, gas, and bloating.

After ovulation (when an egg is released), the second part of the cycle begins - known as the luteal phase. If the egg is not fertilised in the days following ovulation, oestrogen and progesterone will drop, and menses (bleeding) begins.

As this occurs, a group of locally acting hormones known as prostaglandins spike. Prostaglandins cause the uterus to contract and shed its lining, but they also impact the muscles of the gut, which can lead to cramping and diarrhoea(Bharadwaj et al., 2015). The drop in oestrogen and progesterone can also increase sensitivity to pain.

Pregnancy brings its own set of gut health challenges. Remember progesterone? This hormone regulates smooth muscle relaxation, and stays elevated during pregnancy, which can slow the movement of food through the gut. This is thought to help maximise nutrient absorption (excellent for a growing baby!) but can lead to constipation in mum(Gomes et al., 2018). And as constipation often results in straining when pooping, it may increase the risk of haemorrhoids (piles).

Pregnancy hormones relax other muscles in the gut too, including the ring of muscle which connects the oesophagus (food pipe) and stomach. In conjunction with the increased abdominal pressure from the growing baby, this means acid can flow back more easily from the stomach into the food pipe, causing painful heartburn. Pregnancy nausea and sickness is also extremely common, affecting up to 80% of pregnant women. Once again this is thought to be due to pregnancy hormones (Gomes et al., 2018).

Further down the gut, the mum-to-be’s gut microbes undergo changes thanks to oestrogen, which regulates the makeup of the gut microbiome. Research shows that the microbiome changes most dramatically during the third trimester, when oestrogen is at its peak. Specific microbes which help break down the natural sugars in breast milk are increased in the mother’s gut (Turjeman et al., 2021), in preparation for the transfer of microbes from mum to baby during birth (clever huh?).

Later in life, menopause signals a huge hormonal change, often triggering a change in gut health too. Defined as the time when a woman’s periods have stopped for 12 months, menopause (and the time leading up to it - known as perimenopause) is characterised by declining levels of oestrogen and progesterone, alongside an increase in the stress hormone cortisol.

This shift in hormones is responsible for many of the physical symptoms of menopause (think hot flashes and insomnia) but has also been linked with changes in bowel habits (both constipation and diarrhoea) and an increase in symptoms like heartburn.

But it’s not just gut function - there’s also an interplay between declining oestrogen levels and gut microbes. Oestrogen has a beneficial effect on the diversity of the gut microbiome, and this falls after the menopause. However, certain gut microbes (known collectively as the estrobolome) have the capacity to reactivate oestrogen, sending it back into the body (Chen & Madak-Erdogan, 2016). When this process is impaired through changes in microbiome diversity, circulating oestrogen levels can change. But because both excess and low levels of oestrogen are linked with different health conditions, getting the right balance is important.

More research is needed to understand this interplay, but over time, it’s hoped that a better understanding may improve menopause treatments and potentially impact the risk of health conditions which are increased with menopause, by targeting the gut bacteria(Chen & Madak-Erdogan, 2016). In the meantime, eating a diverse diet, rich in lots of different plant foods and fibre, can help to protect the diversity of the gut microbiome.

Changes in gut health can be uncomfortable but understanding these sex-specific shifts can help demystify changes when they happen and encourage you to experiment with steps to ease symptoms. So, for example, if you experience diarrhoea around your period, you might experiment with adjusting caffeine and fibre intake around this time.

Lastly, though fluctuating hormone levels can be a trigger for changes in gut health, it’s always important to discuss a persistent change in your bowel (poo) habits or prolonged gut symptoms that last longer than a couple of weeks with your doctor, to check there’s no underlying condition. They can also discuss the potential for medications that might help with symptoms, and referrals onto a dietitian for support with dietary changes.

Bharadwaj, S., Barber, M. D., Graff, L. A., & Shen, B. (2015). Symptomatology of irritable bowel syndrome and inflammatory bowel disease during the menstrual cycle. Gastroenterology Report, 3(3), 185–193. https://doi.org/10.1093/gastro/gov010

Bolnick, D. I., Snowberg, L. K., Hirsch, P. E., Lauber, C. L., Org, E., Parks, B., Lusis, A. J., Knight, R., Caporaso, J. G., & Svanbäck, R. (2014). Individual diet has sex-dependent effects on vertebrate gut microbiota. Nature Communications, 5. https://doi.org/10.1038/ncomms5500

Chen, K. L., & Madak-Erdogan, Z. (2016). Estrogen and Microbiota Crosstalk: Should We Pay Attention? Trends in Endocrinology and Metabolism, 27(11), 752–755. https://doi.org/10.1016/j.tem.2016.08.001

Gomes, C. F., Sousa, M., Lourenço, I., Martins, D., & Torres, J. (2018). Gastrointestinal diseases during pregnancy: What does the gastroenterologist need to know? Annals of Gastroenterology, 31(4), 385–394. https://doi.org/10.20524/aog.2018.0264

M.T., B., L.A., G., L.E., T., P., R., C.N., B., L.A., S., K., D., & L., A. (2014). Gastrointestinal symptoms before and during menses in healthy women. BMC Women’s Health, 14(2), 1. http://www.biomedcentral.com/1472-6874/14/14

Meleine, M., & Matricon, J. (2014). Gender-related differences in irritable bowel syndrome: Potential mechanisms of sex hormones. World Journal of Gastroenterology, 20(22), 6725–6743. https://doi.org/10.3748/wjg.v20.i22.6725

Turjeman, S., Collado, M. C., & Koren, O. (2021). The gut microbiome in pregnancy and pregnancy complications. Current Opinion in Endocrine and Metabolic Research, 18, 133–138. https://doi.org/10.1016/j.coemr.2021.03.004