Perimenopause
Your gut bacteria recycle oestrogen — and menopause changes which bacteria are doing it
Some of your oestrogen never really leaves. A set of gut bacteria intercepts it on the way out and sends it back into circulation — and a new review pulls together what happens to that system when oestrogen falls at menopause.
The idea has a name: the estrobolome. It refers to the gut bacterial genes that make enzymes — chiefly beta-glucuronidase, alongside beta-glucosidase and sulfatase — capable of undoing the packaging the liver puts on oestrogen for disposal. The liver tags used oestrogen so it can be excreted; these bacterial enzymes strip the tag off in the gut, and the freed hormone is reabsorbed through the intestinal wall and returned to the bloodstream to be used again. It is a recycling loop, and gut bacteria hold one end of it.
That makes the relationship two-way, which is the review's central point. Oestrogen influences which bacteria thrive; those bacteria in turn influence how much oestrogen stays in circulation. So when oestrogen falls at menopause, the gut community shifts too — and the shift is not just cosmetic, because part of what is changing is the machinery that decides how much of your remaining oestrogen gets a second pass.
What actually changes is more specific, and more mixed, than the headline suggests. Several studies in the review report lower Shannon diversity — a standard measure of how varied a bacterial community is — in postmenopausal women, though one Spanish study found no difference in overall diversity at all. The more consistent finding is a shift in the balance: a reduced Firmicutes-to-Bacteroidetes ratio, with Firmicutes, Roseburia, Ruminococcus, Bifidobacterium animalis and Akkermansia muciniphila among the taxa depleted, and Bacteroidetes, Prevotella, Tolumonas and Sutterella wadsworthensis among those enriched. Those last two names are not household words, and that is rather the point: this is early-stage mapping, not a diagnosis anyone can hand you.
On what to do about it, the review is more useful than most. Higher-fibre, lower-glycaemic-index diets correlated with a lower burden of menopausal symptoms. A 12-week low-fat, plant-based vegan diet improved hot-flush severity, and Mediterranean-style patterns were linked to better mood and fewer vasomotor symptoms. Phytoestrogens — the plant compounds in soy and flaxseed — come with a real caveat: isoflavones offer vasomotor, bone and urogenital benefits, but the effect is typically modest next to HRT, and the clearest reductions in hot-flush frequency and severity showed up only in "equol producers", the minority of people whose gut bacteria can convert the soy compound daidzein into its more active form. Whether you are one of them is decided by bacteria you did not choose.
Two honest limits before anyone reorganises their kitchen. This is a narrative review — it synthesises other people's work rather than testing anything, and its authors say plainly that studies demonstrating a causal relationship "remain few and nascent". Microbiome features also vary by geography and ethnicity, which the authors flag as a real confound for associations drawn mostly from Western populations. And on the strain-specific probiotics the field is most excited about, their own conclusion is that large-scale clinical trials are still needed to confirm efficacy and safety. The practical takeaway is not a supplement or a test — it is fibre, plants and a Mediterranean-leaning pattern, which happens to be the advice that was already worth following for blood sugar and for the heart.
What the research says
The estrobolome is the set of gut bacterial genes encoding beta-glucuronidase, beta-glucosidase and sulfatase. Beta-glucuronidase deconjugates glucuronidated oestrogens in the intestinal lumen, allowing reabsorption across the intestinal epithelium and return to systemic circulation — the enterohepatic recycling loop. The review describes the relationship between oestrogen signalling and the gut microbiota as bidirectional.
Lim et al. · Nutrients, 26 March 2026 · Narrative review ↗Multiple studies report a lower Shannon diversity index in postmenopausal women, though one Spanish study found no difference in alpha or beta diversity. A reduced Firmicutes/Bacteroidetes ratio is the more consistent finding, with Firmicutes (fold-change 0.551), Roseburia (0.707), Ruminococcus, Bifidobacterium animalis and Akkermansia muciniphila depleted, and Bacteroidetes (1.43), Tolumonas (1.18), Prevotella and Sutterella wadsworthensis enriched. The authors note that microbiome profiles and symptom prevalence both vary by geography and ethnicity, and that causal studies remain few.
Lim et al. · Nutrients 2026, 18(7), 1052 ↗Related reading
Frequently asked questions
Should I get a microbiome test to check my estrobolome?
No — there is nothing clinically actionable to do with the result yet. The review is describing associations, not a validated test with a treatment attached to it, and the authors are explicit that causal studies are few and that large trials are still needed before strain-specific interventions can be recommended. The advice that comes out of this research is broad and low-risk: plenty of fibre, a wide range of plants, and a Mediterranean-leaning pattern.
Do soy or flaxseed work as a replacement for HRT?
Not as a replacement. Isoflavones do show vasomotor, bone and urogenital benefits in the research the review covers, but the effect is typically modest compared with hormone therapy. There is also a personal lottery involved: the clearest reductions in hot-flush frequency and severity were seen in "equol producers" — people whose gut bacteria convert the soy compound daidzein into a more active form — and not everyone has those bacteria. Soy and flaxseed are worth eating as food; they are not a substitute for a conversation about HRT.
The information on this website is educational and is not medical advice. Please consult your doctor if you have any doubts or further questions.