Soy Beneficial for Breast Cancer Survivors: Study

Dec. 9 -- TUESDAY, Dec. 8 (HealthDay News) -- Regular, moderate consumption of soy foods can help lower the risk of death and cancer recurrence in women who've had breast cancer, new research shows.

What's more, the association between soy and a reduced risk of death held true even for women with estrogen receptor-positive cancers and women taking tamoxifen, according to the study published in the Dec. 9 issue of the Journal of the American Medical Association.

"We found that women with a history of breast cancer who consumed moderate amounts of soy food were doing better in terms of prognosis. They had reduced mortality and reduced recurrence," said study author Dr. Xiao Ou Shu, a professor of medicine and a cancer epidemiologist at Vanderbilt University Medical Center in Nashville, Tenn.

There has been some concern that soy might increase the risk of breast cancer or worsen the prognosis for women already diagnosed with the disease because soy is what's known as a phytoestrogen. That means that it can act like a weak form of estrogen in the body.

However, it appears those concerns may have been unfounded because Shu and her colleagues found that soy actually reduces the availability of naturally occurring estrogen by binding to its receptors.

"In our study, we found that soy food has a very similar effect to tamoxifen," said Shu. Tamoxifen is a drug that blocks the action of estrogen in the body, which can be helpful for treating cancers that are fueled by estrogen.

Shu's study included just over 5,000 Chinese women who had been previously diagnosed with breast cancer between 2002 and 2006. The women were aged 20 to 75, with the majority of women between 40 and 60 at the time of diagnosis.

The researchers collected information on cancer diagnosis and treatment, lifestyle factors (including diet) and disease progression at six months after diagnosis, and then again at 18, 36 and 60 months after diagnosis.