Perimenopause and Digestion: Why Bloating, Constipation and Reflux Can Start in Your 40s

You're eating the same way you always have. You haven't changed much. But suddenly, in your early to mid-40s, you're bloating after meals you used to tolerate fine. You're more constipated than you ever were. You're getting reflux that seems to come from nowhere. And your GP says everything looks normal.

If this sounds familiar, what's often being missed is the profound effect that shifting hormones have on the gut.

Oestrogen and the gut: a relationship most people don't know about

Oestrogen and progesterone don't just regulate your menstrual cycle and reproductive health - they have receptors throughout the gastrointestinal tract. This means that when these hormones fluctuate and eventually decline during perimenopause, your gut feels it.

Research published in the International Journal of Women's Health explains that oestrogen directly influences intestinal motility, mucosal permeability, and the composition of the gut microbiome. As oestrogen declines during the perimenopause transition, these functions can all be disrupted.

What happens to your gut microbiome during perimenopause

Studies consistently show that microbiome diversity (the range of different bacterial species living in your gut) declines as oestrogen drops. Lower diversity is associated with increased bloating, slower digestion, and reduced nutrient absorption.

Interestingly, after menopause, the gut microbiome begins to more closely resemble that of a man of the same age, a pattern sometimes described as 'masculinisation' of the gut. This shift involves a reduction in Firmicutes (bacteria involved in fermenting fibre into nourishing SCFAs) and changes in Bacteroides and Prevotella populations, which are associated with inflammation and metabolic change.

Why progesterone affects your bowel habits: perimenopause and digestion

Progesterone has a direct effect on gut motility, the speed at which food moves through your digestive system. Multiple studies have shown that gut transit time is measurably longer in the luteal phase of the menstrual cycle, when progesterone is generally more dominant. In perimenopausal women, particularly those experiencing anovulatory cycles (where ovulation doesn't occur and progesterone isn't produced), this effect can become more pronounced, contributing to constipation, bloating, and the sense that food is just sitting there.

Falling progesterone also reduces gut motility, which increases fermentation time in the gut. This excess fermentation produces more gas, which means more bloating and sometimes reflux.

The gut barrier changes too

Both oestrogen and progesterone help maintain the integrity of the gut lining. As these hormones decline, intestinal permeability can increase, sometimes referred to as 'leaky gut.' This allows inflammatory signals to enter the bloodstream, which may contribute to the low-grade inflammation many women notice during the perimenopause transition: joint aches, skin changes, heightened sensitivities, and digestive discomfort.

What actually helps

The good news is that dietary and lifestyle strategies can meaningfully support gut health during this transition:

• Prioritising diverse plant foods (30+ plant varieties a week is a useful target for microbiome diversity)

• Increasing fibre: particularly prebiotic foods like garlic, leeks, asparagus, oats, and green bananas, to support beneficial bacteria

• Phytoestrogen-rich foods (flaxseeds, soy, legumes) offer a gentle hormone-modulating effect via the gut

• Managing stress, which independently affects gut motility and barrier function (more on this in a future post)

• Functional gut testing, including microbiome analysis, to understand what's specifically happening for you

Perimenopause is not simply a reproductive transition, it's a whole-body shift that includes the gut. Understanding that is often the beginning of feeling considerably better.

If your digestion has changed in your 40s and you're not sure why, a discovery call is a good place to start. I work with women through personalised 12-week programmes that look at hormones, gut health and the connection between them.

Bella Dorey is a BANT-registered nutritional therapist and qualified Lifecode GX nutrigenomics practitioner, offering stool, blood and DUTCH hormone testing as part of personalised nutrition programmes. Based in Bury St Edmunds, available online across the UK. Book a free 20-minute discovery call to find out whether hormone testing is right for you.