Over the course of your life, your gut microbiome will change significantly. One of the most noticeable changes occurs when you switch from drinking milk to consuming food as a baby. Interestingly, when women reach adolescence, there’s a further change to the microbiome where it becomes more adult-like, however this does not occur in males. Research has suggested that this discrepancy is likely due to the presence of female sex hormones (particularly oestrogen and progesterone) which help to shape our gut microbiomes throughout life. It is for this reason that researchers believe male and female gut microbiomes take very different courses throughout our lifetime.
What is the relationship between the gut and hormone balance?
Gut health and hormonal balance share a bidirectional relationship, with each system influencing the other's function. The gut microbiota, a complex community of microorganisms residing in the digestive tract, plays a pivotal role in this interaction. These microbes metabolise and produce hormones, impacting hormone levels in the body. For example, certain gut bacteria can metabolise hormones which will affect its circulating levels, which in turn can influence various physiological processes. On the other hand, hormones can change the gut environment, affecting factors such as gut motility, permeability, and microbial composition. Imbalances in gut bacteria have been linked to dysregulation of hormones such as oestrogen and cortisol, contributing to conditions such as menstrual irregularities, mood disorders, and metabolic dysfunction.
In addition to microbial metabolism of hormones, the gut-hormone relationship is further refined by the presence of specialised cells in the gut lining known as enteroendocrine cells. These cells produce various hormones and peptides that regulate appetite, metabolism, and digestion. For instance, the release of peptide YY (PYY) and glucagon-like peptide 1 (GLP-1) from enteroendocrine cells in response to nutrient intake influences satiety and insulin secretion, which in turn will affect metabolic processes. Furthermore, gut-derived hormones such as serotonin, often referred to as the "happy hormone," not only play a role in mood regulation but also impact gut motility and function.
Where do sex hormones come into it?
As mentioned, it is understood that the gut microbiome differs significantly between males and females, and has been attributed to the presence of female sex hormones. However, we also know that the levels of circulating hormones in the body are influenced by the gut microbiota, creating a bidirectional relationship.
The primary oestrogens circulating in the female body include estrone, estriol, and estradiol which travel around the body and travel to the liver. Upon reaching the liver, these hormones undergo metabolism, during which they become irreversibly bound to other compounds, which means they become inactive and are no longer able to affect cells in the way they previously would have done. Once bound, they are then excreted from the body. However, importantly, within the gut, certain bacteria have the ability to "recycle" these oestrogens by releasing them from their bound state, allowing them to re-enter the bloodstream again. This phenomenon is not limited to oestrogens but is also understood to occur with other hormones such as progesterone and androgens, such as testosterone. Therefore, it appears that there is a symbiotic relationship between hormones and gut bacteria, where hormones support the growth of specific bacterial species in the gut, and in turn, these bacteria facilitate the reabsorption of hormones into the bloodstream for reuse.
While the research around hormones and gut health in women is still far and few, an interesting study conducted in Austria looked at the effect of taking hormonal contraception on the gut microbiome. The hormones in birth control pills suppress our own body's production of oestrogen and progesterone through a negative feedback loop mechanism. Sixteen individual women who were taking hormonal contraception were studied. It was found that the decreased levels of these hormones in the body was linked to a reduced gut microbiome diversity. An example of this was the observation of lower numbers of Eubacterium, some of which are considered ‘good’ gut bacteria, like E. eligens. The results also showed that throughout the menstrual cycle, the levels of bacteria in the gut fluctuated, which provides us with further evidence that hormones have a profound influence on our gut bacteria.
Navigating life's hormonal milestones: menstrual cycle, pregnancy, and menopause
Menstrual cycle
The menstrual cycle, a recurring process characterised by fluctuating levels of oestrogen and progesterone, is thought to influence gut function in various ways. We say ‘thought to’ as there is reason to believe this is true, however, the scientific evidence is still lacking to prove this effect. Nevertheless, during menstruation, elevated levels of these hormones can affect gut motility and sensitivity, leading to symptoms such as bloating, abdominal discomfort, and changes in bowel habits. Additionally, fluctuations in hormone levels throughout the menstrual cycle can influence gut microbiota composition and function, which may contribute to gastrointestinal symptoms experienced by some women during certain phases of their cycle.
Pregnancy
Pregnancy represents another major hormonal milestone, characterised by significant shifts in hormone levels to support foetal development. The impact of these hormonal changes extend beyond reproductive organs and can affect various physiological systems, including the gut. Pregnancy sees oestrogen and progesterone slowly rising until they reach their peak in the third trimester. These changes in hormone levels can again influence gut motility, leading to symptoms like constipation or diarrhoea. On the other hand, changes in gut microbiota composition during pregnancy have been observed which has been found to have an association with substantial weight gain and significant changes in metabolism and immune defences during pregnancy. However, this may not necessarily be a bad thing, as research suggests that these physiological changes may be completely necessary for foetal development. For these reasons, maintaining gut health during pregnancy is crucial for supporting maternal well-being and ensuring optimal nutrient absorption for foetal development.
Menopause
Menopause occurs when your body's levels of oestrogen and progesterone are too low to continue the natural menstruation cycle. We know that higher levels of the female sex hormones oestrogen and progesterone actually boost gut bacteria diversity by feeding them, which in turn has positive effects on our general gut health. Therefore, the reduction in these hormones during the menopause could be negatively impacting our gut health as we age. As oestrogen levels decline during menopause, women may experience changes in gut function and gastrointestinal symptoms such as bloating, abdominal discomfort, and alterations in bowel habits. Additionally, hormonal changes during menopause can impact body composition, metabolism, and overall health, highlighting the importance of supporting gut health during this transitional phase, especially if it is suppressed.
Again, research in this area is incredibly limited and of the studies that do exist, mixed results have been found. However, a review conducted in 2022 of 10 studies looking into the effect of menopause on the gut microbiome gave insight into what could be going on. The review stated that overall, research suggests that menopause is associated with a lower gut microbiome diversity which in turn produces a shift toward a greater similarity to the male gut microbiome, again providing evidence that the male and female gut microbiome are incredibly different.
Interestingly, oestrogen is also understood to alter visceral sensitivity, which is a characteristic of irritable bowel syndrome (IBS). Researchers have therefore suggested that female sex hormones, specifically oestrogen, could be the reason why IBS is twice as likely to affect women than men. Additionally, it is well understood that IBS incidence declines in women of an older age, and researchers have linked this with the natural decline in oestrogen levels which is associated with menopause.
Lifestyle factors and gut-hormone balance
Incorporating lifestyle factors into the discussion of gut health and hormonal balance is essential for supporting your health and well-being. Regular physical activity, adequate hydration, and avoidance of harmful habits like smoking and excessive alcohol consumption play significant roles in maintaining a healthy gut microbiota and hormonal equilibrium. Exercise, for instance, has been demonstrated to positively influence gut microbiota diversity and function, while chronic stress and poor sleep habits can disrupt hormonal balance and gut health. By emphasising the importance of these lifestyle choices, individuals can take proactive steps towards optimising their gut-hormone relationship and overall health.
How to look after my gut health during these times?
By recognising the influence of hormonal fluctuations on gut function and microbiota composition, women can take proactive steps to support their gut health throughout these transformative stages of life. Prioritising a balanced diet, regular physical activity, stress management, and targeted interventions to support gut health can help women navigate these hormonal transitions with greater ease and maintain overall well-being.
Research suggests that dietary choices significantly influence gut microbiota composition and function. Incorporating a diverse array of fibre-rich foods, eating the rainbow and aiming for thirty different plants a week (such as fruits, vegetables, whole grains, and legumes) promotes gut microbial diversity and enhances gut health. Fermented foods like yoghurt, kefir, and sauerkraut provide beneficial probiotics that support gut microbiota balance. However, as we know, the ‘one-size fits all’ approach does not exist in the world of health and nutrition which is why we highly recommend that you consult a professional dietitian or nutritionist, alongside your healthcare provider to ensure you receive the best possible advice that is tailored to you.
While the diet-first approach should be prioritised to keep your gut thriving throughout womanhood (from menstruation, through pregnancy to the menopause) we understand that due to many reasons such as food intolerances, preferences and dietary requirements, as well as the well-known side effects of pregnancy, food-first simply may not be possible. For this reason, we highly recommend looking into taking a high quality supplement like Symprove, which delivers billions of bacteria to your gut in a morning shot and works to balance your microbiome.
Summary
At the moment, scientific evidence suggests that there is a bidirectional relationship between the gut microbiome and hormones in the body, which interact with each other to alter the state of one another. We know that the female sex hormones (i.e, oestrogen and progesterone) fluctuate hugely throughout our life, and research is starting to emerge to suggest that these fluctuations and imbalances could be having positive and negative effects on our gut health at different stages. However, the caveat is, we don’t quite know what this means for our health and well-being right now. But what we do know is the more diverse your gut microbiome is, the more capable and resilient it is. A greater diversity of microorganisms in the gut is directly correlated with gut and overall health and well-being. Eating plenty of both prebiotic and probiotic foods, and supplementing if you require it, will help promote the most ideal balance between good and bad gut bacteria and keep your gut thriving through these times!
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