A plant-based diet offers some hope for a hard-to-treat form of breast cancer, when it’s combined with a new treatment currently under investigation.

A vegan diet naturally supplies lower amounts of an amino acid called methionine, which is oversupplied in meat-centered diets, and so it may help slow the growth of tumors in patients who have what is known as “triple-negative breast cancer” cells, according to scientists at the University of Wisconsin Carbone Cancer Center, reporting in the journal Clinical Cancer Research. The reason the vegan diet helps is because it primes the cancer cells to be more easily killed by a targeted antibody treatment, a new form of immunotherapy currently undergoing clinical trials.

Patients with triple negative breast cancer currently have limited treatment options because their tumor cells lack the three receptors — estrogen, progesterone and human epidermal growth factor receptor 2 (HER-2) — commonly targeted in hormone or chemotherapy. “What’s particularly exciting about our findings is that they suggest that a dietary intervention can increase the effectiveness of a targeted cancer therapy. We still have much to learn, but we believe that uncovering the molecular effects of specific nutritional interventions like a low- methionine diet will open up new treatment options for cancer,” says Vincent Cryns, the lead researcher. The hope for immunotherapy responders is that diet, combined with the new treatment, will boost the survival time.

The best part of using a plant-based diet to boost the effectiveness of this breast cancer treatment is that it’s both safe and has no side effects, and in the meantime reduces the risk of other diseases such as heart disease and diabetes.

Important note: if you are undergoing treatment for breast cancer, you should not make dietary changes without consulting your doctor.