[Phytoestrogen and cancer prevention].

Phytoestrogens are defined to be plant chemicals that modify estrogenic effects in the body by binding to the estrogen receptors in mammals. Isoflavones, coumestane, lignan, and prenylflavones are examples of these, with isoflavones from soy foods and lignans from rye being a major dietary contribution. Mechanisms of cancer prevention by these phytoestrogens are reviewed, and human epidemiological studies, especially for breast and prostate cancers, are summarized and the results discussed.