Recent studies reveal that bacteria in our gut can recycle discarded sex hormones back into the bloodstream. Researchers found that individuals in industrialized societies host significantly more bacteria that perform this recycling than those in hunter-gatherer populations or non-industrialized farmers. This phenomenon may lead to elevated blood levels of certain sex hormones, presenting potential health risks.

“We don’t yet know how the body reacts to this increased input,” explains Rebecca Britten from Jagiellonian University School of Medicine in Poland. “However, the implications could be substantial.”

Sex hormones, including estrogen, travel in the bloodstream. Elevated hormone levels trigger a chemical signal in the liver, causing the hormone to be excreted via the intestines. Bacteria feed on a sugar molecule attached to the hormone, utilizing an enzyme named β-glucuronidase to remove this tag.

Once the tag is cleaved, hormones can be reabsorbed by the body and re-enter the bloodstream. Research indicates that a notable portion of excreted sex hormones undergoes this recycling process due to gut bacteria.

The term “oestrobolome,” introduced in 2011, refers to the collection of intestinal bacteria that influence estrogen levels. Recently, the term “Testbolome” was proposed, indicating gut bacteria’s role in altering testosterone levels as well.

The latest research, conducted by a British team, analyzed gut microbiome data from various populations, including hunter-gatherers in Botswana, rural farmers in Venezuela, and urban residents in Philadelphia and Colorado. The findings show that the estrogen recycling ability of gut microbes in industrialized populations is up to seven times greater and twice as diverse compared to hunter-gatherers or rural communities.

Interestingly, the study also highlights that formula-fed infants exhibit up to three times more recycling capacity and eleven times more diversity than breastfed infants. However, factors such as age, gender, and BMI did not significantly affect the oestrobolome composition.

Researchers are now investigating if the enhanced recycling capabilities linked to gene sequences translate to actual increases in estrogen levels in the bloodstream. It remains to be seen whether the body compensates for heightened recycling by adjusting hormone levels.

If certain individuals maintain high estrogen levels due to their microbiome, it could significantly impact fertility and overall health, potentially raising the risk for conditions like certain cancers. Conversely, increased recycling might be beneficial for those with low estrogen levels. “We shouldn’t automatically assume that higher estrogen recycling is detrimental,” Britten notes. “In some cases, it can be advantageous.”

Katherine Cook, a professor at Wake Forest University School of Medicine studying the microbiome’s connection to breast cancer risk, emphasizes the growing evidence of gut microbiome’s role in human health. However, she cautions that the current study’s cohort is primarily based in the United States, suggesting that including a European group could strengthen the findings.

Britten expresses her intention to explore the lifestyle factors contributing to these observed differences. “We want to gather more precise data for further research,” she remarks.