Soy Isoflavones Are Not a Risk to Breast-Cancer Survivors

For awhile now, women who have survived breast cancer have worried and wondered about whether it's okay for them to eat soy. Are soy foods safe for them to eat, or do they increase survivors' chances of having a recurrence?

The reason for these concerns is that certain organic compounds found in soybeans, called isoflavones, in fact have certain properties in common with estrogen.

Now, however, a new study done by researchers at the Vanderbilt University Medical Center, and presented in April at the 102nd annual meeting of the American Association for Cancer Research (AACR) in Orlando, Fla., is supplying some answers to this troubling question--answers, I'm pleased to report, that will put many women's minds at ease about this topic. Lead investigator Xiao Ou Shu, M.D., Ph.D., professor of Medicine, notes,

"… soy foods have both estrogen-like and anti-estrogen effects. There are concerns that isoflavones may increase the risk of cancer recurrence among breast-cancer patients because [these women] have low estrogen levels due to breast cancer treatment. We have been concerned that isoflavones may compromise the effect of tamoxifen on breast-cancer treatment because both tamoxifen and isoflavones bind to estrogen receptors."

All participants in the study were breast-cancer survivors, and the researchers compared the outcomes of two groups of these volunteers:

• those who consumed the highest amounts of soy isoflavones (over 23 milligrams [mg] per day)
• those with the lowest soy intakes (0.48 milligram per day or less)

The researchers found that the women who were consuming the most isoflavones had a 9 percent reduced risk of mortality and a 15 percent reduced risk for recurrence, compared to those who consumed the least. (By the way, women in the U.S. consume an average of 3.2 milligrams of soy isoflavones a day.)

So, it sounds like it might be okay for us to stop debating this issue!