New Research Defies Soy-Breast Cancer Links

A new research study has linked soy consumption to reduced recurrence of breast cancer in breast cancer survivors. The research was presented at this month’s 102^nd annual meeting of the American Association for Cancer Research.

Because soy isoflavones can carry estrogenic properties, soy consumption is often thought to be unsafe for estrogen-sensitive breast cancer cells. But data collection from over 16,000 women who participated in the Shanghai Breast Cancer Survival Study; the Life After Cancer Epidemiology Study; the Women’s Healthy Eating and Living Study; and the Nurses’ Health Study suggest that soy may not increase one’s risk.

Researchers used data from 16,048 women, 20 to 83 years old, with histories of invasive primary breast cancer. Soy intake was assessed on an average 13 months after cancer diagnosis, with food frequency questionnaires conducted for soy isoflavones, tofu and soy milk. Incidence of breast cancer was assessed at an average nine years after cancer diagnosis.

High intake of soy isoflavones was considered to be 23 mg per day or higher and low soy intake was considered to be 0.48 mg per day or lower. Compared to subjects with low soy isoflavone intake, subjects with high intake exhibited a 15% reduced risk of breast cancer recurrence and a 9% reduced risk of breast cancer-related death.

The researchers warned, however, that these results did not meet statistical significance; they could be due to chance. Still, the results fall in line with numerous other studies establishing soy’s safety in relation to breast cancer.

“Our results indicate it may be beneficial for women to include soy food as part of a healthy diet, even if they have had breast cancer,” said lead researcher Xiao Ou Shu, MD, PhD, professor of medicine at Vanderbilt University Medical. “This can’t be directly generalized to soy supplements, however, as supplements may differ from soy foods in both the type and amount of isoflavones.”

The American Association for Cancer Research has stated that research on soy and tamoxifen-a prescription drug for breast cancer treatment-would be presented later during the annual meeting.

For the record, Shu and his research team concluded that average daily soy intake among women in the United States was 3.2 mg compared to 45.9 mg for women in Shanghai.