The gut hormone connection: why your microbiome controls your oestrogen

There is a specific subset of bacteria in your gut that controls how much oestrogen circulates in your body. It is called the estrobolome, and almost no one has heard of it, even though it sits at the centre of nearly every perimenopause symptom you have ever had. The gut hormone connection is not a metaphor. It is an enzyme pathway, and the bacteria running it respond to what you eat.

What is the gut hormone connection? The estrobolome is the collection of gut bacteria that produce an enzyme called beta-glucuronidase, which deconjugates oestrogen in the intestine and sends it back into circulation. When these bacteria are well fed with fibre and fermented foods, oestrogen clearance is regulated. When they are disrupted, oestrogen either builds up or drops too fast, and the symptoms follow.

I have written about the gut microbiome broadly in the complete guide to gut health after 40, and about how fermented foods like kefir support the microbiome. This post is about a narrower and more specific question: how the gut controls your oestrogen, and what that means when your ovaries are winding down.

How the estrobolome works: the enterohepatic loop

Oestrogen does not leave your body in a straight line. It follows a loop, and the gut is the turning point.

When your liver processes oestrogen, it attaches a sugar molecule to the hormone through a process called glucuronidation. This packages the oestrogen for elimination, marking it as waste to be excreted through bile into the intestine. So far, so straightforward. The complication is that certain gut bacteria produce an enzyme called beta-glucuronidase, which snips that sugar molecule back off. When the sugar comes off, the oestrogen is reactivated, reabsorbed through the intestinal wall, and sent back into circulation. This is the enterohepatic loop, and it is the mechanism by which your gut decides how much oestrogen stays in your bloodstream.

The term for the bacterial community that does this is the estrobolome, coined by researchers studying the gut-oestrogen axis. A 2025 review by Blair and colleagues in the International Journal of Cancer (PMID: 40177842, review article) maps the specific microbial taxa and enzymes involved, establishing the estrobolome as a measurable, functionally distinct subset of the gut microbiome rather than a vague concept.

The key insight is that beta-glucuronidase activity is not fixed. It changes with diet, with antibiotics, with stress, and with the hormonal transitions of perimenopause. A 2023 review by Chen and colleagues in Microbial Cell Factories (PMID: 37559394, review article) set out the regulatory role of gut microbial beta-glucuronidase in female oestrogen metabolism, noting that both the abundance of the bacteria and the expression of the enzyme respond to dietary inputs.

In other words, the amount of oestrogen circulating in your body is not just a function of what your ovaries produce. It is also a function of what your gut bacteria do with it after the liver has tried to remove it.

What happens in perimenopause: the feedback problem

Here is where it gets interesting, and slightly unfair.

In perimenopause, oestrogen production from the ovaries becomes erratic. Some months are high, some are low, and the overall trend is downward. You would think the gut would just adjust, but the relationship runs in both directions. Oestrogen itself shapes the gut microbiome. A 2025 review in Nutrients by Lim and colleagues (PMID: 41978103, review article) synthesises the bidirectional relationship between oestrogen and the gut microbiome, noting that gut dysbiosis underlies several menopause-related symptoms through inflammation and altered hormone metabolism.

So falling oestrogen changes the gut microbiome, and a changed gut microbiome handles oestrogen differently, which can amplify the very symptoms you are trying to manage. The hot flushes, the mood swings, the brain fog, the weight redistribution: none of these are purely ovarian events. They are the product of a system in which the gut is a major player, and in perimenopause that player is being asked to operate with less information and fewer resources.

A 2025 paper by Liu and colleagues (PMID: 40551890, narrative review) frames the gut microbiota as an overall regulator of women’s oestrogen status during menopause, noting that microbial diversity drops as oestrogen falls, and that this drop is an untapped target for improving postmenopausal health. The earlier foundational review by Baker and colleagues, published in Frontiers in Microbiology in 2017 (PMID: 28778332, review article), established the physiological framework for the oestrogen-gut microbiome axis and its clinical implications.

This is why the same woman can eat the same diet at 38 and 45 and feel like a completely different person. The food has not changed. The gut bacteria processing it have.

If you want the wider context on how this fits into the hormonal picture, the post on perimenopause nutrition and eating when your cycle disappears covers the practical dietary angles.

The three dietary levers that move the estrobolome

The good news is that the estrobolome responds to food, and the mechanisms are well enough understood that you can target it directly. Three levers matter.

Lever one: fibre. The bacteria that produce beta-glucuronidase are fibre-dependent. When fibre intake is adequate, these bacteria are abundant and regulated, and oestrogen recycling operates in balance. When fibre intake is low, microbial diversity drops, the balance shifts, and oestrogen metabolism becomes less stable. The Lim review (PMID: 41978103) notes that dietary fibre is the primary modulator of the gut microbiome’s capacity to process oestrogens, and that low-fibre diets are associated with altered oestrogen profiles in postmenopausal women. The target is roughly 30g daily, which is more than most adults in the UK eat, but achievable with lentils, oats, vegetables, and whole grains.

Lever two: fermented foods. Fermented foods support the broader microbial diversity that the estrobolome sits within. This is not about a single probiotic strain that fixes oestrogen. It is about maintaining the diverse ecosystem that allows the estrobolome to function as part of a balanced community. The Sunday prep system I wrote about in the post on the 7-day biological age reset includes a fermented cabbage jar for exactly this reason: daily fermented food is one of the most consistent levers for gut diversity, and gut diversity is what the estrobolome needs.

Lever three: cruciferous vegetables. Cabbage, broccoli, cauliflower, and Brussels sprouts contain compounds called glucosinolates, which the body converts to indole-3-carbinol and then to diindolylmethane (DIM). These compounds support the liver’s glucuronidation pathway, the same pathway that packages oestrogen for elimination. By supporting the packaging end of the loop, you help ensure that the oestrogen your liver marks for removal is actually removed, rather than reactivated by gut bacteria and sent back into circulation. You do not need vast quantities. Three servings a week is enough to meaningfully support the pathway.

A simple weekly plan for the estrobolome

Nothing here requires supplements or specialist products. The estrobolome responds to ordinary food, consistently eaten.

Daily: One serving of fermented food. A spoonful of sauerkraut, a small glass of kefir, or a serving of kimchi. This is the diversity lever.

Daily: 30g of fibre. A bowl of lentils, a serving of oats, two or three servings of vegetables, and a handful of walnuts gets you there. This is the substrate lever.

Three times weekly: Cruciferous vegetables. Broccoli with dinner, coleslaw at lunch, roasted Brussels sprouts alongside a Sunday roast. This is the glucuronidation lever.

That is the whole system. Three foods, consistent timing, no supplements required.

If you already have a meal prep routine, the five jars system is a good framework for keeping these foods available through the week without thinking about it daily.

Where this fits

The gut hormone connection is one of the mechanisms that makes perimenopause harder than it needs to be, and it is also one of the most responsive to food. You cannot control what your ovaries are doing, but you can shape the gut bacteria that decide what happens to the oestrogen your body still produces.

This is exactly the kind of mechanism that The Cellular Reset is built around. The eight-week programme puts the estrobolome-supporting foods into a personalised meal plan alongside the methylation and biological age frameworks, so the gut, the hormones, and the methylation cycle are addressed as one system rather than separate problems. It costs £97, with nothing to cancel afterwards. If you want the science first, The Cellular Reset ebook covers the same ground for £7.

The science behind the programme explains how the Fitzgerald trial showed a 3.23-year reduction in biological age over eight weeks using a food-first approach (DOI: 10.18632/aging.202913, pilot RCT).

Start with the fermented food. The rest follows.

This content is for informational purposes only and does not constitute medical advice. Always consult your GP or qualified healthcare professional before making changes to your diet, supplement regimen, or lifestyle, particularly if you are pregnant, breastfeeding, taking medication, managing a health condition, or considering hormone replacement therapy.