Dietary Approaches for Breast Cancer Treatment

Conventional breast cancer treatment—surgery, radiation, chemotherapy—may be less effective when they stand alone. Complementary lifestyle approaches may help reduce the side effects of cancer treatment, improve physical and emotional well-being, and improve recovery from cancer.

“What integrative cancer care should be doing is integrating knowledge from all aspects of medicine and health—epidemiology and public health, nutritional medicine, endocrinology, as well as oncology and complementary medicine—into the care of cancer patients. The key is not to think ‘outside the box’ but to create a ‘bigger box,’” says Dr. D. Barry Boyd, MD, MS, a pioneer in the field of integrative cancer care with a focus on nutritional support for cancer patients.

There is clinical evidence behind two dietary patterns that may support conventional cancer treatment: the fasting-mimicking diet and the ketogenic diet.

The Fasting-Mimicking Diet

Evidence suggests that short-term fasting and fasting-mimicking diets may protect healthy cells from the stressors of chemotherapy. Research suggests that fasting causes healthy cells to switch from a proliferative state toward a state of maintenance and repair. Because fasting deprives proliferating cancer cells of nutrients, growth, and other factors, this may make them more sensitive to cancer therapy and increase cell death.

A 2020 randomized controlled trial of 131 patients looked at the effects of fasting-mimicking diets on toxicity and efficacy of chemotherapy in cancer patients, and the results suggest that fasting-mimicking diet cycles are safe and effective as an adjunct to chemotherapy in women with early breast cancer. Fasting periods of at least 48 hours may be required to induce a robust decrease in circulating glucose, IGF-1, and insulin levels.

A clinical trial in 2021 looked at patients who were treated with different types of therapies, including chemotherapy, endocrine therapies, proteasome inhibitors, and more, and found the fasting-mimicking diet was also feasible and safe. When combined with dietary and muscle training instructions to promote weight and lean body mass re-gain in the periods between fasting-mimicking diet cycles, the fasting-mimicking diet decreased fat mass and effectively lowered circulating insulin, IGF-1, and leptin levels.

More recently, scientists studied a calorie-restricted, five-day fasting-mimicking diet regimen and its metabolic and immunomodulatory effects on cancer patients and found that fasting-mimicking diet cycles may decrease the side effects and increase the effectiveness of chemotherapy. 

The Ketogenic Diet

The ketogenic diet is a high-fat, low-carbohydrate diet with adequate protein. This diet may sensitize most cancers to standard therapy. Studies suggest that in combination with standard therapies, the ketogenic diet may improve the antitumor effects of conventional chemotherapy and improve quality of life. New evidence suggests a ketogenic diet lowers the level of glucose and insulin in the blood, which are necessary for tumor growth.

A 2021 systematic review looked at ketogenic diets and their therapeutic potential on breast cancer and found that the ketogenic diet improves biochemical parameters and body composition. However, another 2021 systematic review points out that a ketogenic diet may be considered a controversial treatment for cancer patients, and found that there was no conclusive evidence that ketogenic diets had anti-tumor effects or improved overall survival.

Although clinical evidence for the effectiveness of ketogenic diets in cancer patients is still lacking, and more research is necessary, this therapeutic option should be a consideration for highly motivated patients who are willing to adhere to the ketogenic diet.