Diets high in soy and cruciferous vegetables may alleviate some symptoms associated with breast cancer treatments, recent research suggests.
The potential benefit was found for people who consume edamame or soy-based foods, such as soy milk and tofu, and cruciferous vegetables, such as cabbage, kale, Brussels sprouts and broccoli, according to a study by researchers at Georgetown Lombardi Comprehensive Cancer Center. Lead author Sarah Oppeneer Nomura, PhD, and her colleagues presented the findings in Breast Cancer Research and Treatment.
Breast cancer remains the second most common cancer among American women, behind skin cancer, according to the American Cancer Society (ACS). Thanks to advances in detection and in treatments, including radiotherapy and chemotherapy, the death rate from female breast cancer dropped 39 percent from 1989 through 2015, averting almost 323,000 breast cancer deaths. The United States today has approximately 3.1 million breast cancer survivors, the ACS notes.
However, many women experience long-term side effects, such as fatigue, early menopause or menopausal symptoms, and failure to address side effects adequately may have life-threatening consequences.
“These symptoms can adversely impact survivors’ quality of life and can lead them to stopping ongoing treatments,” Nomura stated in a news release from Georgetown University Medical Center. “Understanding the role of lifestyle factors is important because diet can serve as a modifiable target for possibly reducing symptoms among breast cancer survivors.”
Nomura’s cross-sectional study examined the dietary habits of 192 Chinese-American women and 173 non-Hispanic white American women. To qualify for the study, each woman had to have been diagnosed with stage 0–3 breast cancer and undergone primary cancer treatment.
Researchers conducted telephone interviews to gather information about common side effects the participants were experiencing, such as hot flashes, night sweats, fatigue, thinning hair and memory problems. They used questionnaires to gather data about the subjects’ intake of soy and cruciferous vegetables. Soy intake among the women varied from 0 to 431 grams per day, while consumption of cruciferous vegetables ranged from 0 to 865 grams per day.
After analyzing the data, researchers discovered that women who had higher soy intake were 49 percent less likely to report having menopausal symptoms and 57 percent less likely to report fatigue, according to a Medical News Today article about the findings. Heavier consumption of cruciferous vegetables was also linked to a 50 percent reduced risk of menopausal symptoms.
The findings build on earlier research suggesting an association between soy consumption and alleviation of side effects related to breast cancer treatment. A 2007 study published in Menopause, the journal of The North American Menopause Society, found that women who received an extra 60 mg of isoflavones — the main effective compounds in soybeans — experienced a 43 percent reduction in night sweats and a 57 percent reduction in hot flashes.
Researchers attributed this correlation to the fact that isoflavones in soy products can function like estrogen and thus help relieve certain menopausal symptoms.
A Note of Caution
Physicians may not yet want to recommend their breast cancer patients undertake significant dietary changes based on the findings from the more recent study. Scientists at Georgetown University agree that further research is needed to understand the relationships between soy and cruciferous vegetables and side effects of breast cancer treatment.
Moreover, the benefits of higher consumption of certain foods were not equally dispersed. For example, the reductions in menopausal symptoms and fatigue found in the Georgetown study were statistically significant only among non-Hispanic white participants. Researchers venture that this could be in part because Chinese women generally do not report as many menopausal symptoms.
Patients who do not eat soy products should not begin doing so until additional research provides greater clarity about potential benefits and risks, Leena Hilakivi-Clarke, PhD, co-author of the study, stated in the news release.