What we do (and don't) know about the estrobolome

Your liver spends part of every day packaging up estrogen your body has finished with and sending it out through your gut. Most of that estrogen leaves, but some of it doesn't because certain gut bacteria make an enzyme that can cut those packages open, freeing the estrogen to be reabsorbed instead.

That bit of biology is called the estrobolome, and over the past two years, it has been popping up more and more frequently in advertising. But our experts this week caution that data on the estrobolome thus far doesn’t really exist.

Once estrogen has done its job, your liver binds it to a molecule that marks it for disposal and sends it to the gut to leave the body. But some gut bacteria carry an enzyme called beta-glucuronidase, which can cut this bond. This means some of that estrogen can be reabsorbed instead of leaving the body, says Harsha Moole, MD. 

In recent years, more and more marketing have been targeted toward our ability to influence this process. Some claim that their probiotics can "nurture the estrobolome" to maintain steady estrogen levels as ovarian production drops or that they can prevent "estrogen dominance" and flush out "toxic" estrogen, but Dr. Gillian Goddard, board-certified endocrinologist and author of The Hormone Loop says she wouldn't trust any of the claims made in marketing. “We don't know enough to know if any of these products are useful,” she says.

The short answer is that no human trial has shown that changing your gut bacteria meaningfully changes your estrogen levels or your menopause symptoms. Moole says: “The enzyme is real. The pathway is real. It has been shown in lab work and in animal studies. What is not established is the part everyone repeats, which is that you can meaningfully move your own estrogen levels by changing your gut.”

Observational studies cannot establish which came first, and these comparisons are tangled up with diet, body weight, age, antibiotics, and geography. The studies also compare the gut bacteria of women with a condition like endometriosis, PCOS, or breast cancer against women without it, adds Moole. While they find differences, Moole says, “That is an association. It does not tell you which came first.”

Moole says that claims in the supplement and at-home-testing market don’t hold up: “What the test gives you is a snapshot of which bacteria are present, and sometimes a beta-glucuronidase estimate from a stool sample, which is not the same as what is happening in your body.”

"Estrogen dominance" works the same way: it sounds like a measured lab value and functions as a marketing label. Supplements sold as a natural estrogen modulator, such as DIM, calcium D-glucarate, are recommended far more confidently than the evidence supports. "If a product claims to fix your hormones through your gut, ask for the trial that measured hormones. It will not be there,” says Moole.

If you’ve recently read that your gut controls your hormones, Moole would tell you that menopause is driven by the ovary, not by the microbiome. “That does not mean the gut is unimportant. It means the gut is the back office, not the control panel,” says Moole. 

Whether or not the estrobolome story turns out to be important, the basics are still what matter most when it comes to supporting our hormones: Enough protein and resistance training to hold onto muscle and bone, sleep, moderating alcohol, fiber, and a conversation with a trusted provider about HRT if you want to go that route. 

At the end of the day eating well is good for your gut. Not necessarily because it’s going to reset your hormones, but because it’s a foundational part of good health in general. And perhaps your estrobolome will thank you in the future.

The information provided about wellness and health is for general informational and educational purposes only. We are not licensed medical professionals, and the content here should not be considered medical advice. Talk to a doctor before trying any of these suggestions.