The so-called gut “microbiome” has gotten a lot of attention for its effect on one’s digestive health and its impact on chronic diseases. But researchers have now discovered that microorganisms that comprise the microbiome also live in breast tissue…and the implications could be significant when it comes to breast cancer risk.

Study details: As a stand-in for human subjects, researchers studied 38 female monkeys—half of whom were fed a typical American diet (high in unhealthy fats and refined carbohydrates)…with the other half receiving a plant-focused Mediterranean diet.

Results: After two and a half years (the equivalent of about eight human years), the groups had significantly different bacteria in their breast tissue. Compared with the standard diet group, the Mediterranean-diet monkeys had more bile acid metabolites and about 10 times as much Lactobacillus in their breasts—both of which have been shown to reduce breast cancer risk.

Why it matters: While the microbes that live in the human digestive tract have been well-researched, this is the first time that the breast gland has been found to have a microbiome and that it, like the gut microbiome, can be affected by diet. An imbalance in the gut microbiome has previously been linked to inflammatory bowel disease, irritable bowel syndrome, obesity and even type 2 diabetes.

“We were surprised that diet directly influenced microbiome outside of the intestinal tract in sites such as the mammary gland,” explained Katherine Cook, PhD, assistant professor of surgery, hypertension and cancer biology at the Medical Center, a part of Wake Forest Baptist Medical Center. “However, we are just at the early stages of understanding how dietary effects on the microbiome might be used to protect women from breast cancer.”

Researchers are digging deeper: More studies are under way to determine whether supplements such as fish oil and probiotics can affect the breast microbiome. Results from those studies may be a few years away.

Takeaway: Even though this research is preliminary, you don’t have to wait to eat a Mediterranean diet, including plenty of fruits and vegetables, whole grains, legumes, nuts, olive oil and more fish than red meat. In addition to its potential to improve your breast flora, this diet has been shown to lower levels of LDL “bad” cholesterol, reducing heart disease risk.


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