Herbal Necessities

The three major isoflavones found in soybeans are genistin, daidzin, and glycitin. Soy isoflavones exert both estrogenic and anti-estrogenic effects, depending on the tissue in which they are acting. They are structurally similar to 17-estradiol, a mammalian estrogen, and are thus called phytoestrogens. They also have non-hormonal effects, including signal transduction and antioxidant activity. Soy isoflavones may inhibit bone resorbption and help stimulate bone formation,2 without the side effects of hormone replacement therapy.

In recent years there has been an increase in the number of basic science, clinical, and nutritional studies investigating the potential health effects of phytoestrogens.3 Genistein is the most abundant phytoestrogen, derived almost entirely from soybeans, and is proposed to be the most biologically active. In postmenopausal women in the U.S., the daily intake of genistein is only about one mg per day.4 The Japanese however, who consume about 50 mg per day, are the longest-lived people in the world.5