ABSTRACT
Phytoestrogens are nonsteroidal plant-derived compounds, structurally similar to endogenous estrogens, but capable of showing both estrogenic and antiestrogenic effects (Setchell, 1998). Although their effects are not totally understood, it has been postulated that phytoestrogens may exert antiestrogenic effects in high-estrogen environments and have weak estrogenic effects in lowestrogen environments (Messina, 1999). Phytoestrogens are divided into four main groups: isoflavonoids, flavonoids, coumestans, and lignans. While the main food source of isoflavones is the soybean, flavonoids are more widely distributed in vegetables, fruits, berries, herbs, and green tea; coumestrol, the main dietary coumestan, is found in alfalfa sprouts and beans; and lignans precursors are present in fiber-rich foods, such as flaxseed and unrefined grain products (Strauss et al., 1998).
