Our industrialized, modern lifestyles may be increasing how much estrogen (the female sex hormone) gets recycled in our bodies, according to a study published in the journal Proceedings of the National Academy of Sciences. And it appears to be down to the increased abundance and diversity of specific bacteria in our gut.
Estrogen is a steroid hormone that is involved in regulating fertility, growth and metabolism. When the liver processes estrogens, it adds a tag called glucuronic acid, which deactivates the hormone and makes it water-soluble so it can be excreted. However, a group of gut bacteria known as the estrobolome can strip that tag off, reactivating estrogen and allowing it to be reabsorbed by the body.
In this latest study, scientists discovered that the capacity of these bacteria to recycle estrogen is significantly higher in industrialized populations than in non-industrialized ones.
Analyzing gut bacteria
The research team analyzed previously collected gut microbiome data from 24 different populations across four continents. This included a wide range of lifestyles, such as city dwellers in the United States and hunter-gatherers and farmers in Africa, Asia and South America.
Specifically, the team was looking for genetic sequences linked to beta-glucuronidase enzymes, which are the tools bacteria use to strip the tag off estrogen. By measuring the abundance and variety of these sequences, the scientists could estimate the recycling capacity of the gut microbes within each human population.
They found that people living in industrialized societies have up to seven times greater capacity to recycle estrogen than those in non-industrialized groups, and more than double the variety of these hormone-recycling bacteria. A similar pattern was also seen in how we feed our youngest, as the team notes in their paper: “Industrialized populations, as well as formula-fed infants, have greater microbial capacity for estrogen recycling than nonindustrialized populations and breastfed infants.”
Low-fiber diets as a possible cause
Why modern living appears to drive these changes is not fully understood, and the researchers don’t dive into the exact causes in their paper. But they speculate that it may be linked to low-fiber diets. In the absence of fiber, gut bacteria may turn to alternative fuel sources. Some begin feeding on the mucus lining of the intestine, while others can break down glucuronic acid from deactivated hormones like estrogen. This may explain why the estrogen recycling capacity appears higher in industrialized populations.
Regardless of the exact cause or mechanism, the discovery adds to a growing body of work about the importance of the gut microbiome. “These findings demonstrate that industrialization and early-life feeding may strongly influence microbial contributions to human estrogen metabolism and exposure,” the researchers conclude.
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Publication details
Rebecca S. A. Brittain et al, Industrialization increases the estrogen-recycling capacity of the gut microbiome, Proceedings of the National Academy of Sciences (2026). DOI: 10.1073/pnas.2523589123
Journal information:
Proceedings of the National Academy of Sciences
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