Millions of women across the world are diagnosed with breast cancer every year. Treatments developed over the last decades have greatly improved survivorship as well as return to a cancer-free life for many. Even so, 650,000 women globally died from the disease in 2020.

New research suggests that breast cancer has links to changes in the gut and mammary microbiota. The microbiota at these sites appear to influence risk, response to treatment, and recurrence.

Follow the Science

I recently conducted a comprehensive review of research on the potential role of microbes in prevention and treatment of breast cancer for The International Probiotics Association. There are two parts:

Part 1: Microbes & Breast Cancer focuses on how the gut and mammary microbiota and related dysbiosis (disrupted microbiota) may impact breast cancer risk (tumor formation and progression).

“The complex relationships between the gut and mammary microbiota and breast cancer are far from understood. The evidence presented here supports further study of the unique microbial characteristics in breast cancer, understanding its carcinogenesis, pathogenicity, or symbiosis in the tumor microenvironment. Strategies to modulate and sustain changes in gut microbiota, via dietary, prebiotic and/or probiotic supplementation show potential in the management of breast cancer risk.”

Part 2: Microbes & Breast Cancer Treatments looks at recent findings that suggest implications in treatments including surgery, radiation, and systemic therapies.

“Medical research has made impressive gains against breast cancer. The extensive menu of treatments— surgery, radiation, and systemic therapy —have improved survival from this, unfortunately, common disease. Yet the treatments don’t always work the same for everyone and are often accompanied by severe side effects. Recent research suggests that gut microbiota may modulate cancer treatments’ efficacy as well as ameliorate certain adverse effects.

The manipulation of microbiota to select certain types of microorganisms— with the support of prebiotics and probiotics, for example—offers a potential strategy to improve response and lessen toxicity to various cancer therapies.”


Breast cancer is a beast. The research linking both the gut and mammary microbiota to risk, response to treatment and recurrence is compelling. Every woman— and man— will benefit by getting ahead of this common cancer. If you have already been diagnosed, the information provides a concise picture of treatments as well as tools for improving outcomes. Be well.