Study Sheds Light on How Certain Foods May Impact Breast Cancer

David Litman/ShutterstockMany factors play a role in breast cancer risk—genes, exercise, and hormones are just a few. While it’s less clear how certain foods may impact breast cancer, there is some evidence that adding certain cancer-fighting foods to your diet might help.

In a 2017 study, researchers at the University of Alabama at Birmingham looked at how compounds in green tea and broccoli sprouts affected laboratory-grown breast cancer cells and tumors in mice. When these compounds were combined and administered as a dietary treatment to mice, their tumors were converted from estrogen receptor-negative to estrogen receptor-positive, which means the cells could respond (and in theory, be treated) with the estrogen-inhibiting drug, tamoxifen, according to their report in the journal Scientific Reports. 

About three-fourths of all invasive breast cancers have estrogen receptors (ER) on their surface, so they are called ER-positive, according to Trevan D. Fischer, MD, a surgical oncologist and an assistant professor of surgical oncology at the John Wayne Cancer Institute at Providence Saint John’s Health Center in Santa Monica, California. This means the cancer cells grow in response to the hormone estrogen, and they can be targeted by hormone therapy that binds to the receptor and thus slow or stop the tumor’s growth. The less common form of breast cancer is ER-negative, and it’s much less likely to respond to hormone therapy because there’s no receptor on the surface to attach to the hormone therapy drug.

“ER-negative breast cancer does not have the estrogen receptor, therefore, the treatments with anti-estrogen pills, like tamoxifen, do not work,” Dr. Fischer explains. “If the breast cancer also does not have HER2, a different receptor that has [a] specific drug that can target the cancer, it is called triple-negative breast cancer, which is more aggressive, but can respond to traditional chemotherapy.” Triple-negative breast cancer makes up about 10 to 15 percent of all breast cancer.

In the study, the researchers identified two substances in common foods that might be beneficial in terms of cancer prevention: Sulforaphane from cruciferous vegetables such as broccoli and cauliflower, and polyphenols, found in green tea. (Find out more about the health benefits of green tea.) The dietary concentrations used in mice were equivalent to one to two cups of green tea and two cups of broccoli sprout/per day for human consumption.

The University of Alabama researchers work in the field of epigenetics, the study of biological mechanisms that can switch genes on and off. Their hope is to identify ways to alter gene expression in diseases such as ER-negative breast cancer, potentially overriding the cancer’s imperviousness to hormone therapy. While conventional cancer research tends to zero in on a single compound, the researchers have been combining cancer-preventive compounds in attempts to target ER-negative tumors.

The study can’t really say if a particular diet will help women with the disease since there’s no guarantee that compounds that affect laboratory-grown cells would have the same impact in the body. (See what happens to your body when you follow a vegan diet.) However, further research could potentially introduce new treatment options for patients in human clinical trials.

Nutrition plays a key role in cancer care and finding ways to use your diet to supplement the effect of traditional breast cancer medication is very promising, according to Dr. Fischer. “A plant-based diet will likely only work in combination [with] other treatments and may not work in everyone,” he says. “At this point, it should not be used as a substitute for other treatment.”

The next step would be to take these findings and test them in human clinical trials, the researchers concluded.