Gut bacteria shown to break down oestrogen and reduce breast cancer risk

Postmenopausal women with diverse gut bacteria have a reduced risk of breast cancer according to research published in the Journal of Clinical Endocrinology & Metabolism (Associations of the Fecal Microbiome with Urinary Estrogens and Estrogen Metabolites in Postmenopausal Women. Journal of Clinical Endocrinology & Metabolism).

It has long been known that plasma oestrogenic compounds like oestradiol are linked to breast cancer risk (and other cancers such as prostate, some brain, lung and colorectal cancers).

It is also now known that a loss of diversity in the gut microbiome can be linked to increase rates of illness; and for more than 40 years it has been known that certain gut bacteria ‘process’ oestrogenic products. This new study involving just 60 postmenopausal women between the ages of 55 and 69 enrolled in Kaiser Permanente Colorado (the study will be redone involving larger numbers) has shown that a loss of diversity in the gut microbiome is linked to a greater risk of breast cancer. “Our findings suggest a relationship between the diversity of the bacterial community in the gut, which theoretically can be altered with changes in diet or some medications, and future risk of developing breast cancer” said James Goedert, MD, of the National Institutes of Health’s National Cancer Institute (NCI) in Bethesda.

“We are hopeful that, because the microbiome can change the way the body processes oestrogens, it may one day offer a target for breast cancer prevention”.

The bacterial colony determine the denaturing and processing of ‘dangerous oestrogens’ and what is left behind or excreted.

“In women who had more diverse communities of gut bacteria, higher levels of oestrogen fragments were left after the body metabolized the hormone, compared to women with less diverse intestinal bacteria.”