What Are Soy Isoflavones Used For?

Soy is a controversial food. It is a major cash crop for U.S.-based agricultural conglomerates like Archer-Daniels Midland. These companies assert that the estrogen-mimicking activity of soy isoflavones can prevent some types of cancers. At the same time, researchers in Israel and the U.K. have cited numerous health risks associated with soy and soy isoflavones. Definitive answers to the controversy remain elusive.

Identification

• Soybeans are the most concentrated source of isoflavones in the human diet. Isoflavones are phytoestrogens, which means they are plant-based substances that have estrogen-like effects in the body. The two major soy isoflavones are daidzein and genistein.

Metabolism

• The biological activity of soy isoflavones is largely dependent on how they are metabolized. Bacteria in the intestines of roughly one third of Western populations break down daidzein into a less estrogen-like compound.

Anti-Estrogenic Activity

• The most interesting action of soy isoflavones is their ability to mimick estrogen in some tissues and block the effects of estrogen in others. This anti-estrogenic activity is viewed as potentially reducing the risk of hormone-associated cancers of the breast, uterine and prostate.

Health Risks

• While soy isoflavones are touted as being potentially beneficial, it is also known that soy is a goitrogenic food, meaning it inhibits iodine uptake and reduces thyroid function. The Israeli Health Ministry has recommended only moderate consumption of soy because of its links to several disorders including digestive trouble, ADHD, reproductive problems and cancer.

Controversy

• The British Dietetic Association studied soy and evidence about its supposed health benefits. It found that soy isoflavones increase the risk of breast cancer and can reduce male fertility. The panel also concluded that evidence suggesting soy isoflavones reduce the symptoms of menopause is inconsistent.