Is Soy Really Better?
The question is coming up more and more these days. Are soy products really healthy additions to a person's diet and are they safe as a hormone-replacement therapy, or are they cancer-causing agents? The answer might be best worded: It depends.
Isoflavones and Their Effects
William Helferich, University of Illinois food science and human nutrition professor has spent a long time, at least 10 years, evaluating the health effects of isoflavones, a class of plant estrogens present in high concentrations in soy. He focused much of his work on a single isoflavone, genistein, which occurs in varying degrees of concentration in soy products, tofu, soy protein isolates, soy flour and some estrogenic dietary supplements. Genistein is the most active of the soy isoflavones. It activates estrogen receptors in cells, including some breast tumor cells.
The many different studies done on the effects of soy have delivered varying and seemingly contradictory findings. Some of the findings indicated that genistein fed to female rats prior to puberty reduced the number of chemically induced mammary tumors while other studies showed that estradiol, a primary human estrogen, spurs the growth of existing estrogen-dependent breast tumors.
Helferich demonstrated that genistein responds like estradiol by stimulating the growth of estrogen-responsive tumors. They also found that treatments for cancer, such as tamoxifen, which target estrogen receptors in the breasts, are hampered by genistein.
"Natural" Hormone Replacement
These days, William Helferich focuses his attention on the use of genistein and other isoflavones in so-called "natural" supplements sold as alternatives to hormone-replacement therapy. They are assumed to be safe by women in midlife, however, women 50 years of age and over are more at risk for developing breast cancer. Many women are taking these supplements without prescriptions and in a wide variety of forms. The biological activity and implications of these supplements are important to know for the safety of the women taking them.
Drop in HRT Use = Drop in Breast Cancer Rates
The rate of incidence of breast cancer in women of the age of 50 and older dropped significantly in the US after there was a decline in the use of HRT in 2002 and 2003. While genistein is not as potent as HRT, it still poses a problem in that women take it in much larger quantities. Because it is a natural product, it is hard to master quality control, so potency may vary.
The Good Side of Soy
The picture would be incomplete without examining the positive effects of soy. Genistein is only one component and misleading conclusions may result if the scope is not broader. Soy flour does not react the same way as genistein. "The complex mixture found in soy flour doesn't make the tumor grow," said Helferich. "Whole soy contains a lot of biologically active ingredients, but together they may have multiple effects that can reduce the negative outcomes. When the whole food is consumed you get a very different effect than if you consume the concentrated constituents individually."
"All of this research points to a very simple truth," Helferich said: "The whole soybean is healthier than many of its individual chemical parts.