Background

• The word "phytoestrogen" is derived from phyto, meaning "plant" and estrogen, because of the ability of these compounds to affect estrogenic activity in the body. Phytoestrogens are a diverse group of polyphenolic, nonsteroidal plant compounds that may cause both estrogenic and antiestrogenic effects. The estrogenic effects of phytoestrogens are similar, although less intense, than those of estrogens made by the human body. There are reportedly approximately 300 plant species containing phytoestrogen compounds that have some degree of estrogen activity.
• The three major classes of phytoestrogens are isoflavones, lignans, and coumestans. Isoflavones are prominent in soy-based foods. Lignans are minor components of cell walls and fibers of seeds, fruits, berries, vegetables, grains, and nuts. Linseed (flaxseed) is a rich source of lignans. The primary coumestan is coumestrol. It is found in alfalfa and clovers, and in low levels in soybeans and peas.
• Several population studies have indicated that phytoestrogens have health benefits. These include possible protection against menopausal symptoms and osteoporosis, as well as a potential reduction in breast cancer, prostate cancer, and cardiovascular disease risks. Both isoflavone and lignan phytoestrogens may have antioxidant activity.

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