A recent study investigated the link between a high soy diet and the incidence of osteoporotic fractures among women who received successful treatment for breast cancer.
Breast cancer is the most common cancer after skin cancer among women in North America and the second-leading cause of death in North American women from all cancers. The most common type of breast cancer is hormone receptor-positive breast cancer, also known as ER-positive breast cancer. Breast cancer treatments can lead to decreased bone mineral density. As a result, women who survive breast cancer have a high probability of osteoporosis-related fracture compared to healthy women of the same age.
Some measures such as food enriched with calcium and vitamin D, exercise and smoking cessation help to avoid osteoporosis; however, the role of a high soy diet is not clear. Soy-based products are high in isoflavones, a class of phytoestrogens that mimic estrogen action and modulate estrogen metabolism. A recent study published in JNCI Cancer Spectrum investigated the link between high soy diet and the risk of osteoporotic fractures among breast cancer survivors.
The study used data from the Shanghai Breast Cancer Survival Study (SBCSS) of 3986 patients from 20 to 75 years, who survived newly diagnosed breast cancer. The number of postmenopausal women was slightly higher than pre-/perimenopausal, at 52%. Researchers gathered detailed information about cancer diagnosis and treatment, body mass index (BMI), dietary habits, exercise and other lifestyle information from medical charts. All selected patients had an in-person follow-up at 18 months and 3, 5, and 10 years after diagnosis to access ongoing health status and changes.
During the 10-year period after the breast cancer diagnosis, breast cancer survivors had 2.5 times more osteoporotic fractures than healthy women. However, the consumption of a high soy diet was associated with the 77% reduction of osteoporotic fractures, but only in younger patients. For postmenopausal women, there were no associated changes suggesting that the intake of high soy diet before menopause helps to prevent osteoporotic fractures.
Among women of all ages in the study, tamoxifen, a medication used for breast cancer treatment, reduced osteoporotic fracture risk by37% among breast cancer survivors, especially with prolonged use. Interestingly, tamoxifen has the same biological effect as a high soy diet, but it helped to reduce osteoporotic fractures in the overall study population regardless of menopausal status.
The researchers hope that the current findings will help to find a new approach in the development of comprehensive recommendations to diminish fracture risk in this population of women.
Written by Anna Otvodenko
Zheng, N., Hsieh, E., Cai, H., Shi, L., Gu, K., Zheng, Y., Bao, P. and Shu, X. (2019). Soy Food Consumption, Exercise, and Body Mass Index and Osteoporotic Fracture Risk Among Breast Cancer Survivors: The Shanghai Breast Cancer Survival Study. JNCI Cancer Spectrum, 3(2).
Breast cancer statistics – Canadian Cancer Society. (2019) [online] Available at: https://www.cancer.ca/en/cancer-information/cancer-type/breast/statistics/?region=on [Accessed 28 May 2019].
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