Scientists and doctors have conflicting information regarding the safety of soy isoflavones for breast cancer survivors. Isoflavones can bind to estrogen receptors and can exert both estrogen-like and anti-estrogenic affects. Genistein is known to activate estrogen receptors in cells, including estrogen-positive breast cancer cells. Many epidemiologic studies have examined the relationship between soy intake and breast cancer risk. These studies give mixed results, but a meta-analyses combining the results of eight of these studies found that higher soy intake was associated with lower breast cancer risk.
Dr Shu and co-workers presented during the 2011 annual meeting of the American Association for Cancer Research their result of study on the safety of soy isoflavones from data from over 16,000 women with diagnosed breast cancer. They concluded that concerns over breast cancer recurrence from consuming isoflavones may be unfounded.
The researchers found that women with the highest intake of soy isoflavones had a 9 percent lower risk of mortality and a 15 percent lower risk of recurrence; however the results were statistically not significant. Dr Shu wrote that it may be beneficial to include soy foods as part of a healthy diet for women, including those which had breast cancer. Dr Shu warns that the result may not work for soy isoflavones supplements, which have different types and levels of isoflavones.
American Association for Cancer Research’s 102nd Annual Meeting 2011