Higher Soy Intake Associated With Lower Risk of Fractures Among Young Survivors of Breast Cancer

Offering diet implications for pre- and perimenopausal survivors of breast cancer, study findings have demonstrated that higher soy intake is associated with a decreased risk of osteoporotic bone fractures. If confirmed, the findings can help guide future risk management strategies for the population, which has a high incidence of osteoporosis-related fractures.

The findings, coming from data from the Shanghai Breast Cancer Survival Study of more than 5000 newly diagnosed breast cancer survivors, revealed that higher soy intake was associated with a 77% reduced risk of osteoporotic fractures among younger women.

“The menopausal transition is known to be a period of high risk for bone loss, and given the relative scarcity of data related to fracture risk among younger women with breast cancer, this study marks an important contribution to this body of literature,” said study lead author Evelyn Hsieh, MD, PhD, assistant professor of Medicine at Yale School of Medicine, in a statement. “Our findings, in particular regarding the protective effects of soy food consumption, provide novel insight into how future interventions can best be tailored to different risk groups.”

The study focused on 4139 women from the study aged 20 to 75 years between March 2002 and April 2006, 1987 of whom were pre- or perimenopausal and 2152 of whom were postmenopausal. In the overall study population, higher soy intake was not associated with fracture risk. Looking at other modifiable risk factors for decreased bone mineral density, the researchers also assessed the impact of body mass index, exercise, and tamoxifen use.

Over a 10-year period, 3.6% of the women experienced an osteoporosis-related fracture, and these women were more likely to be postmenopausal, less likely to exercise, and less likely to use tamoxifen. Meanwhile, there were no observed differences by cancer stage, estrogen receptor—positive status, progesterone receptor–positive status, or other treatment types.

Tamoxifen was associated with a 37% reduced risk of osteoporotic fractures in all women regardless of menopause status, particularly among those with long duration of use. This finding was consistent with prior studies. Tamoxifen is a selective estrogen receptor modulator (SERM), used for the treatment of breast cancer, that causes an increase in bone mineral density. Soy-based foods, which are rich in isoflavones, provide a natural SERM, according to the researchers.

Being overweight was associated with an increased risk of fractures among pre- and perimenopausal women and a marginally reduced risk in postmenopausal women. Meanwhile, exercise was associated with a reduced risk of fractures in only postmenopausal women.

Reference

Zheng N, Hsieh E, Cai H, et al. Soy food consumption, exercise, and body mass index and osteoporotic fracture risk among breast cancer survivors: the Shanghai breast cancer survival study [published online May 21, 2019]. JNCI Cancer Spectr. doi: 10.1093/jncics/pkz017.