When executives for companies that sell soybeans went to the Food and Drug Administration requesting permission to claim that soybeans prevent heart attacks, they didn’t expect the scientific community to start to look for harmful effects from eating soybeans.

Two more studies show that extracts of soybeans, called isolfavones, cause cancer in mice. When isolfavones get into your body, they act like weak estrogens. Estrogen helps strengthen bones and prevent heart attacks, but excessive or prolonged exposure to estrogens causes cancers.

The June issue of the respected medical journal, Cancer Research, shows that injecting genistein into newborn mice for 5 days, causes uterine cancer (1). The doses were only slightly higher than infants receive from drinking soybean milk. In fact, genistein from soybean caused a higher rate of cancer than DES, the artifical estrogen that is an established known cause of uterine and vaginal cancer in humans. The July issue of Nutrition and Cancer will feature an article from the University of Missouri showing that genistein causes breast cancer in mice (2).

I am upset that the Food and Drug Administration allows soybeans to claim that they prevent heart attacks, because some people will think they should eat huge amounts because they are healthful. High doses of anything can expose you to chemicals that harm you. I don’t think that reasonable amounts of soybeans are harmful. A study in the May issue of Cancer Epidemiology, Biomarkers, and Prevention showed that Chinese girls who took in lots of soybean foods had a lower incidence of breast cancer (3). But eating excessive amounts of soybean products or taking soybean extracts may increase your risk for cancer.

1) Cancer Research June 1, 2001.

2) Nutrition and Cancer July, 2001.

3) Cancer Epidemiology, Biomarkers, and Prevention, May 2001.

Checked 5/3/07