Recent research has demonstrated that there is a strong link between the health of your gut and oestrogen regulation. One of the main regulators of oestrogen is in fact our gut microbiome. But this is a two way relationship – circulating oestrogen affects our microbiome which in turn has a significant impact on oestrogen regulation. We become colonised at birth by microbiota, largely bacteria and most of this bacteria (about 90%) lives in our gastrointestinal tract.
Oestrogen Metabolism
Oestrogen is produced by the ovaries, the adrenal glands and adipose tissue. Oestrogen circulates in the bloodstream in its free form or bound to protein and metabolised in the liver. Oestrogen and its metabolites are conjugated in the liver to make them water-soluble so that they can be excreted in urine or in bile in faeces.
The conjugated oestrogen in bile can then be deconjugated by gut bacteria. Our microbiome regulates oestrogen by secreting an enzyme called β-glucuronidase which deconjugates oestrogen into its active form. This leads to oestrogen reabsorption into circulation which can then affect target tissues. This active, unbound oestrogen binds to oestrogen receptors which leads to a number of physiological responses, influencing reproductive processes, neural development, cardiovascular health and cancers.
The oestrobolome affects the excretion and circulation of oestrogen. The activity of β-glucuronidase activity can be modified by diet. Increased feacal β-glucuronidase activity has been associated with people who consume high fat or protein diets. Conversely, eating more fibre will reduce β-glucuronidase activity.
What factors affect the oestrobolome?
The oestrobolome affects the excretion and circulation of oestrogen. The activity of β-glucuronidase activity can be modified by diet. Increased feacal β-glucuronidase activity has been associated with people who consume high fat or protein diets. Conversely, eating more fibre will reduce β-glucuronidase activity.
An oestrobolome which is rich in bacteria that is higher in deconjugative activity will lead to higher circulating oestrogen levels and increased risk of oestrogen dominance. Strict vegetarians have increased faecal excretion of conjugated oestrogen and lower bacterial β-glucuronidase activity . Therefore they will have less circulating plasma oestrogen. Apart from diet, the oestrobolome is also affected by other factors like antibiotic use, alcohol consumption, our genetics and our delivery mode.
Imbalances in the gut microbiome and oestrogen-related disease
So what happens when there is an imbalance in the gut microbiome aka dysbiosis? Well oestrogen metabolism is disrupted when there is a loss in bacteria diversity due to a reduced number of oestrogen-metabolising bacteria. This also has other metabolic effects due to the reduction of short chain fatty acids (SCFAs). Read on here for my blog on SCFAs.
Alterations in circulating oestrogens may contribute to the development of the following conditions: obesity, metabolic syndrome, polycystic ovary syndrome (PCOS), endometriosis, fertility, cardiovascular disease (CVD), cognitive function and cancer eg hormone-driven breast cancer due to states of relative oestrogen excess.
Sex hormones play a role in body fat distribution and how fat cells (adipocytes) differentiate. In postmenopausal women, dysbiosis is linked to increased risk of obesity, osteoporosis and cardiovascular disease (CVD). This is because oestrogen and its receptors play a role in lipid and glucose metabolism. When there is a disruption in this metabolic signalling, increased risk of metabolic syndrome and CVD can occur. Obesity is significantly more prevalent in postmenopausal women due to low circulating oestrogen which is mediated by the gut microbiome (and not just due to endogenous secretion).