THE SOY CONTROVERSY
Some physicians warn their patients not to eat soy foods because they fear that soy may increase the risk of breast cancer instead of decreasing it. Their mistaken fear comes primarily from one study from the University of California, San Francisco published in October 1996. In this study, women were given 38 grams of genistein a day for one year. It’s important to note that these women were not given genistein as it occurs naturally in whole soy foods. Rather, they were given genistein that had been extracted and isolated from soy foods and prepared as a supplement—a supplement composed only of genistein with none of the hundreds of other nutrients in soy.  

The researchers were surprised to discover that instead of having a protective effect, the genistein supplement appeared to be harmful. After one year on the genistein supplement, the women had elevated the amounts of estradiol in their blood and their breast cells showed signs of stimulation and increased growth. This unexpected result concerned researchers. Could soy actually increase the risk of cancer? Hundreds of other studies show that women who eat the most soy have the lowest risk of breast cancer. So, how could a genistein isolate have the opposite effect?  

The women in the controversial study didn’t eat fresh whole soy foods. They were given an isolate of genistein—something that doesn’t naturally occur in Nature. When you isolate a substance from the whole, the isolate often behaves differently. Your body was designed to eat, digest, and metabolize fresh whole foods, which contain hundreds, even thousands, of substances all interacting with one another. Those interactions can be critically important. One substance may balance the effect of another, make it more or less effective, take away its toxic effects, increase its absorption, or modify how your body uses it in some important way.  

Research shows that when genistein is consumed as part of whole soy foods, it’s absorbed very differently from how it is in an isolated supplemental form. Genistein in whole soy is activated by intestinal bacteria during digestion, whereas genistein taken as an isolated supplement is absorbed before it reaches the bacteria in the intestines. This may be part of the reason that genistein supplements appear to have an effect different from that of whole soy foods. So, until research shows otherwise, stay away from genistein supplements and eat whole soy foods.