If your digestion has changed in your 40s – more bloating, more irregularity, a gut that feels harder to manage than it used to – you are not imagining it and it is not just about what you're eating.

The digestive changes that happen in perimenopause are real, common, and almost never properly explained. Most women are told to eat more fibre or reduce stress. Very few are told that declining oestrogen directly affects gut function at a physiological level – and that understanding this connection changes what you should actually do about it.

What is perimenopause?

Perimenopause is the transition period leading up to menopause – typically beginning in the early to mid 40s, though it can start earlier. During this period, oestrogen and progesterone levels fluctuate and gradually decline. Most people focus on the hot flushes, sleep disruption, and mood changes. Far fewer talk about what these hormonal shifts do to the gut.

How oestrogen affects gut function

Oestrogen receptors are found throughout the gastrointestinal tract – in the stomach, small intestine, and large intestine. This means oestrogen directly influences gut function, and when oestrogen levels decline, gut function changes with it.

Gut motility slows down

Oestrogen plays a role in regulating gut motility – the speed at which food and waste move through the digestive tract. As oestrogen declines in perimenopause, motility tends to slow. This is why constipation, bloating, and that uncomfortable feeling of fullness after meals become more common. Food is simply moving more slowly than it used to.

The gut microbiome changes

Research published in the journal Cell Host and Microbe has demonstrated that oestrogen directly influences the composition of the gut microbiome. As oestrogen levels fall, the diversity of gut bacteria tends to decrease. Lower microbiome diversity is associated with increased bloating, irregular bowel habits, greater intestinal inflammation, and reduced production of short-chain fatty acids – compounds that are essential for gut lining integrity and immune function.

Intestinal permeability increases

Oestrogen plays a protective role in maintaining the integrity of the gut lining. As levels decline, the tight junctions between gut lining cells can become less effective – a state sometimes referred to as increased intestinal permeability. This allows bacterial byproducts to cross into the bloodstream more easily, contributing to the low-grade systemic inflammation that underlies many perimenopausal symptoms including joint pain, brain fog, and fatigue.

The oestrogen-gut feedback loop

The relationship between oestrogen and the gut runs in both directions. Your gut doesn't just respond to oestrogen – it also helps regulate it.

A specific collection of gut bacteria called the estrobolome produces an enzyme called beta-glucuronidase, which is responsible for metabolising and recycling oestrogen in the body. When the estrobolome is healthy and diverse, oestrogen metabolism is efficient. When gut health is poor and the estrobolome is disrupted, oestrogen metabolism becomes less effective – which can worsen the hormonal symptoms of perimenopause.

This is one of the most important and least discussed aspects of women's hormonal health. Your gut health directly affects your hormone levels – not just the other way around.

Why progesterone matters too

Progesterone also affects gut function, in a different way to oestrogen. Progesterone has a relaxant effect on smooth muscle – including the smooth muscle of the bowel wall. In the luteal phase of the menstrual cycle, when progesterone is highest, many women notice slower digestion and increased bloating. As progesterone levels become more erratic in perimenopause, these symptoms can become less predictable and more pronounced.

What this means practically

The gut changes of perimenopause are hormonal in origin – which means dietary changes alone often don't fully resolve them. Eating more vegetables or cutting out gluten may help temporarily, but it doesn't address the underlying microbiome shift or the change in gut motility that oestrogen decline is driving.

What does help:

Daily prebiotic fibre

Prebiotic soluble fibre feeds beneficial gut bacteria and supports microbiome diversity – directly counteracting one of the key gut changes that perimenopause drives. The type of fibre matters. High-viscosity fibres like psyllium can worsen bloating in an already sensitive gut. Low-viscosity soluble fibres like PHGG – partially hydrolysed guar gum – provide the same prebiotic benefit with significantly better tolerability.

Hydration and electrolytes

Slower gut motility in perimenopause means the large intestine has more time to absorb water from stool – contributing to harder, drier stools and more difficult bowel movements. Adequate hydration and electrolyte balance – particularly magnesium, sodium, and potassium – supports gut motility and keeps bowel movements comfortable.

Consistency over intensity

The gut microbiome responds to consistent, daily inputs. A fibre supplement taken occasionally does very little. The benefit accumulates with daily use over weeks and months – which is why choosing something genuinely tolerable matters as much as choosing something effective.

A note from a GP

As a doctor, I saw this pattern constantly. Women in their 40s coming in with gut symptoms that had changed – more bloating, more irregularity, a digestive system that felt less reliable – and leaving with advice that didn't address what was actually happening hormonally.

It's one of the reasons I built Sol.ve. I wanted a daily fibre option that was gentle enough to take every day, dissolved properly, and supported the specific gut changes that perimenopause drives – without adding to the bloating and discomfort that many women are already managing.

If your digestion has changed in the last few years and you haven't been able to explain why, this is likely part of the answer.

Written by Dr Louisa Wilkinson, GP and founder of Sol.ve Health.