To see the headlines, "Soy Will Not Increase the Risk of Breast Cancer Relapse," one would think they could start eating all the soy they want. “If you regularly eat soy, you don’t need to worry or avoid it, and women who want to lead a healthy life, can safely include some soy in their diets,” says study researcher Xiao Oh Shu, MD, PhD, a professor of medicine at Vanderbilt Epidemiology Center of Vanderbilt University Medical Center in Nashville, Tenn.
Let's not get ahead of ourselves. Do we believe that consuming moderate amounts of the right type of soy increases the risk of breast cancer relaspe? No, we do not. But this is a perfect example of how not to get ahead of yourself from one study.
The study was performed on 18,312 women from China, not the United States. The type of soy foods Chinese women eat are different than what most women eat in the U.S. In China, fermented soy such as tofu and tempeh are more frequently consumed, whereas in the U.S., soy protein and soymilk are more predominant. Soy protein and soymilk on average have much more concentrated amounts of soy isoflavones.
In addition, soy that is grown in the US is the most heavily sprayed crop with pesticides. This adds xenoestrogenic residue to any product it is made with.
After an average of nine years after their breast cancer diagnosis, women in the study who consumed the highest amount of soy, or more than 23 milligrams of soy per day, had a 9% lower risk of dying from any cause and a 15% reduced risk for breast cancer recurrence, compared to women who consumed 0.48 milligrams of soy per day or less. 23 milligrams per day of soy consumed is the equivalent of one glass of soy milk or a half cup of tofu.
This is good news, but we would still recommend that women who had breast cancer consume organic soy foods whenever possible, and try to stick to fermented soy products only.