The study combined three public gut-microbiome datasets covering 24 populations across four continents, including hunter-gatherers and pastoralists in Botswana, Tanzania and Nepal, rural farmers in Malawi and Venezuela, and urban residents in Philadelphia and St. Louis. One dataset allowed comparison between breastfed and formula-fed infants, giving a view of how early feeding relates to microbial function.
Previous research shows that inactive estrogen is excreted into the intestine, where gut microbes break it down; a substantial fraction of this discarded estrogen can be reactivated by microbes and reabsorbed into the bloodstream. The researchers examined the estrobolome, the specific subset of gut microbes that perform this recycling, to measure its capacity and composition across populations.
They found notable differences in both capacity and diversity. Gut communities in industrialized populations showed up to seven times greater capacity to recycle discarded estrogen into the bloodstream than those in non-industrial populations. Formula-fed infants had two-to-three times the recycling capacity of breastfed infants, and the estrobolome was about 11 times more diverse in formula-fed infants. Overall, estrobolome diversity was roughly twice as high in industrialized groups compared with non-industrial settings, a finding one researcher called surprising given that overall gut diversity is usually lower in industrialized societies.
The lead author said daily environments, diets and everyday habits in industrialized settings may shape hormone-regulating microbes. Researchers now aim to identify the specific factors and to understand how the body responds. Possible contributors include diet, reduced physical activity, improved sanitation and greater access to health care:
- Dietary differences
- Lower physical activity
- Improved sanitation
- Broader health care access
Experts caution it is not yet clear whether increased estrogen recycling is beneficial or harmful. A new project funded by the Polish National Science Foundation aims to answer some of these questions. The study appears in Proceedings of the National Academy of Sciences.
Difficult words
- gut-microbiome — community of microorganisms living in the intestine
- estrobolome — subset of gut microbes that modify estrogen
- pastoralist — a person who raises livestock for a livingpastoralists
- reactivate — cause to become active again after inactivityreactivated
- reabsorb — take back into the body or bloodstreamreabsorbed
- sanitation — measures that keep water and places clean
- diversity — range of different species or types present
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- What health consequences might follow if estrogen recycling increases in a population? Give reasons.
- Which everyday changes (diet, activity, sanitation) do you think could most affect the gut microbes, and why?
- How could researchers test whether increased estrobolome diversity is beneficial or harmful?
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