Functional Medicine · Hormonal Health

The Journal

by Dr. Natasha Ryan, ND

Gut Health · Hormones

The Estrobolome: How Your Gut Bacteria Help Control Your Estrogen

3 min read

Most women think of estrogen as something the ovaries make and the body uses. But there's a second player in the story: the bacteria in your gut. Together, the gut genes that process estrogen are called the estrobolome, and they help decide how much estrogen stays in circulation and how much leaves your body.

How estrogen moves through the gut

After estrogen does its work, the liver packages it for removal. It attaches a molecule that inactivates the estrogen and tags it for disposal, a process called conjugation. The packaged estrogen is sent into the bile and on to the intestines, where it should leave in the stool.

That's where gut bacteria come in. Some of them make an enzyme called beta-glucuronidase, which can unpack that estrogen and turn it back into its active form. Once reactivated, it can be reabsorbed into the bloodstream. This loop between the liver and gut is called enterohepatic circulation.

Why the balance matters

A 2017 review in Maturitas described the gut microbiome as an important regulator of circulating estrogen through this enzyme. The amount of activity matters in both directions:

  • Too little: when the microbiome is less diverse, beta-glucuronidase activity can fall, and less estrogen is recycled. The review links lower estrogen from this pathway with metabolic syndrome, obesity, and cardiovascular disease.
  • Too much: high activity can recycle more estrogen than the body needs, which has been proposed as a contributor to estrogen-driven conditions such as endometriosis and endometrial hyperplasia.

The review is careful to frame these as possible contributions rather than proven causes, and that's the right way to read this research. It's an active area, and the human studies are still relatively small.

What the human studies show

One of the early human studies, published in the Journal of Translational Medicine in 2012, looked at men and postmenopausal women. People with a richer, more diverse gut microbiome had higher levels of estrogen and estrogen metabolites in their urine. The authors concluded that gut bacteria influence non-ovarian estrogen levels, while noting the study was small and needed to be repeated.

Larger work followed. A 2022 study in mSystems, covered in more detail in menopause and the gut microbiome, analyzed stool from more than 2,300 adults in the Hispanic Community Health Study/Study of Latinos. Postmenopausal women had a different gut microbiome from premenopausal women, one that looked more like men's. They also had changes in estrobolome genes, including less beta-glucuronidase, and those microbiome changes were associated with less favorable heart and metabolic profiles.

What this means for you

The estrobolome is one reason gut health and hormone health can't really be separated. It's also why constipation matters more than most women think. When stool sits in the colon longer, there's more time for estrogen to be unpacked and reabsorbed.

The practical steps are the same ones that support the microbiome generally:

  • Eat a wide variety of plants. Fiber feeds a diverse microbiome and keeps stool moving.
  • Stay regular. Daily, complete bowel movements help estrogen leave the body as intended.
  • Include fermented foods. They're one of the few dietary changes shown to increase microbiome diversity in a controlled trial.
  • Use antibiotics only when needed. They can sharply reduce microbiome diversity for a time.
  • Limit alcohol. It affects both the microbiome and how the liver processes estrogen.

Some stool tests report beta-glucuronidase activity. A result is most useful alongside your symptoms and your hormone testing, not on its own.

The bigger picture

Symptoms of estrogen imbalance, like heavy periods, breast tenderness, bloating, and mood swings before your period, have more than one cause. The gut is one of them, along with how the liver processes hormones, body fat, and the natural swings of perimenopause. Looking at all of them together is how you find out which ones apply to you.

References

  1. Baker JM, et al. “Estrogen-gut microbiome axis: Physiological and clinical implications.” Maturitas, 2017. View source
  2. Flores R, et al. “Fecal microbial determinants of fecal and systemic estrogens and estrogen metabolites: a cross-sectional study.” Journal of Translational Medicine, 2012. View source
  3. Peters BA, et al. “Menopause Is Associated with an Altered Gut Microbiome and Estrobolome, with Implications for Adverse Cardiometabolic Risk in the Hispanic Community Health Study/Study of Latinos.” mSystems, 2022. View source