(NewsNation) — Your gut bacteria may influence hormone-related cancer risk, researchers say.

The bacteria living in your gut may play a much larger role in hormone-related cancers than scientists previously believed, according to a new review published in the journal npj Biofilms and Microbiomes.

Researchers analyzed existing studies examining how the gut microbiome — the trillions of bacteria and other microbes that live in the digestive tract — interacts with the body’s hormone system.

While scientists have long known gut bacteria help regulate estrogen, the review suggests the microbiome acts as an active partner in hormone signaling, influencing inflammation, metabolism and immune responses that may affect cancer development.

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Previous research has focused on the “estrobolome,” a group of gut bacteria that produces enzymes capable of reactivating estrogen after the body begins breaking it down. This process can extend the body’s exposure to active estrogen, which has been linked to hormone-driven cancers such as estrogen receptor-positive breast cancer and endometrial cancer.

The review found the microbiome’s role is likely much broader. Depending on the types of bacteria present, gut microbes can either increase or decrease estrogen activity. Factors including diet, medications and overall health may also shape these effects.

Because not everyone has the same mix of gut microbes, researchers say these microbial byproducts could one day help identify people at higher risk for hormone-related cancers or guide more personalized treatments.

Hormonal changes throughout life, including puberty, pregnancy, menopause and hormone therapy, also appear to reshape the microbiome. In turn, changes in gut bacteria may influence hormone levels, inflammation and immune responses.

The review also highlights several ways microbial imbalance, known as dysbiosis, may contribute to cancer. An unhealthy imbalance in gut bacteria has been linked to chronic inflammation, changes in metabolism and altered insulin signaling, all of which may work alongside estrogen to promote tumor growth.

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Some studies suggest breast, uterine and endometrial tissues contain their own microbial communities that may influence local hormone activity and inflammation. Other microbial compounds may damage DNA or affect gene regulation, although the researchers note most evidence in humans remains observational rather than demonstrating cause and effect.

Scientists are also investigating whether changing the microbiome could improve cancer treatment. Potential approaches include probiotics, prebiotics, targeted enzyme inhibitors, live bacterial therapies and fecal microbiota transplantation. Early laboratory studies have shown promise, but researchers caution that these strategies have not yet been proven to prevent or treat hormone-related cancers in people.

Researchers emphasize that more long-term human studies and clinical trials are needed before microbiome-based therapies become part of standard cancer care.

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