Soy isoflavones are classified as phytoestrogens which are found in relatively high concentrations in soybeans. Phytoestrogens are plant-derived nonsteroidal substances that possess estrogen-like biological activity. Soy isoflavones possess both weak estrogenic and weak anti-estrogenic effects. Their presence in soy foods may offer some explanation as to why people living in countries where soy products are a big part of the diet do not suffer from as many or as frequent hot flashes and other menopause related difficulties. It might possibly even explain why rates of certain hormone-linked cancers are lower in Asia than they are in other parts of the world, including the United States.

Two types of isoflavones in soy, genistein and daidzein, may also offer both antioxidant and phytoestrogenic properties which appear to protect against some hormone-related disorders such as breast cancer and endometriosis. They do this by competing for the same place on cells that the body's own estrogen does. Saponins, a similar substance found in soy, enhance immune function and combine with cholesterol whereby inhibiting its absorption by the body. Phytosterols and other substances in soy have also been reported to be helpful in lower cholesterol levels and protecting against heart disease.

Soy isoflavones may aid women and men in maintaining bone mineral density, whereby preventing osteoporosis. Although the use of soy in the prevention of osteoporosis offers hope, no conclusive human studies have substantiated these effects.

Recommended Dosage

The best way to gain the benefits of soy is by having a diet that incorporates substantial amounts of soy. Although there is not suggested intake of soy, researchers suggest that supplementation equivalent of one serving of soy per day is healthy. Societies in which large amounts of soy are consumed ingest from 50 and 100 mg daily of soy isoflavones.