New research from the University of Virginia Comprehensive Cancer Center found that a buildup of bile acids caused by an unhealthy gut can “drive breast cancer to other parts of the body.”

The research helps to explain “how the gut microbiome – the collection of microorganisms that live in and on our intestines – plays a role in the spread of hormone receptor-positive (HR+) breast cancer.” The lead researcher said that “an unhealthy gut microbiome loses the ability to regulate the composition of bile acids, potent signaling molecules that when not properly regulated can cause havoc on your health, metabolism, and the immune system.”

The findings suggest that it is possible to “reduce breast cancer metastasis either by replenishing the bacteria that can modify the composition of bile acids, or by treating breast cancer patients with bile acid sequestrants.”

HR+ breast cancer is “by far the most common form of metastatic breast cancer, with 225,000 diagnoses each year in American women.” It tends to spread early, “with tumors often forming in the lymph nodes and lungs.” This research identifies a specific mechanism responsible for resultant gut microbiome imbalances. Elevated bile acids and insulin resistance were associated with reduced survival in mice.