Industrial Lifestyles Alter Gut Bacteria's Estrogen Processing, Study Finds

A new study provides evidence that industrialized lifestyles are changing how people regulate estrogen and other hormones through the gut microbiome—the ecosystem of microbes inside the digestive system. The gut microbiome plays a critical role in regulating estrogen, a hormone that influences fertility, growth, development, and susceptibility to conditions such as breast and ovarian cancer.

According to the study, the gut microbiomes of people in industrialized societies have up to seven times greater capacity to recycle discarded estrogen into the bloodstream than those of individuals in non-industrial populations. The findings also showed that formula-fed infants have two-to-three times the capacity to recycle estrogen than breastfed babies, suggesting that differences in how gut microbiomes process estrogen begin early in life.

“It is really striking that industrialized lifestyles and early life infant feeding choices may be unintentionally influencing our hormone levels through the gut microbiome. Our daily environments, diets, and habits in industrialized society appear to affect the levels of gut microbes that regulate hormones.”

Rebecca Brittain, lead author and former postdoctoral research fellow in Yale University’s anthropology department and at the Jagiellonian University Medical College in Poland, emphasized the need for further research. “The next step is to pinpoint the specific factors driving these differences and understand how the body responds to this hormone recycling,” she said.

The study, published in the Proceedings of the National Academy of Sciences, was coauthored by Richard Bribiescas, a professor of anthropology at Yale, and Grazyna Jasienska, professor of health sciences at the Jagiellonian University Medical College.

Study Methodology: Analyzing Gut Microbiomes Across Populations

For the study, researchers analyzed three publicly available gut-microbiome datasets, covering 24 populations across four continents. These included hunter-gatherers and pastoralists in Botswana, Tanzania, and Nepal; rural farmers in Malawi and Venezuela; and urbanites in Philadelphia and St. Louis. One dataset specifically included information on the gut microbiomes of breastfed and formula-fed infants.

Prior research established that inactive estrogen is excreted into the intestine and broken down by microbes. A significant percentage of this discarded estrogen is reactivated and reabsorbed into the bloodstream. The new study found that the microbial composition of the estrobolome—the subset of the gut microbiome responsible for breaking down discarded estrogen—is 11 times more diverse in formula-fed infants than in breastfed infants. It is also twice as diverse in people from industrialized populations compared to those in non-industrialized settings.

This latter finding is particularly surprising, as previous research has shown that gut microbiomes in industrialized societies are typically less diverse due to reduced exposure to environmental bacteria. Richard Bribiescas noted that the study’s results suggest lifestyle and environment significantly influence hormone regulation and lifetime exposure to estrogen.

“Further study is needed to pinpoint the specific causes of greater estrogen recycling in industrialized populations, but diet is likely an important factor. Other contributing factors could be reduced physical activity, improved sanitation, and greater access to healthcare.”

Bribiescas added, “Understanding these mechanisms could have significant implications for public health, particularly in addressing hormone-related diseases.”