The two primary isoflavones in soybeans are daidzein and genistein. Soybeans and soy foods have attracted much attention because they are unique as the only nutritionally significant dietary sources of isoflavones. Isoflavones may directly inhibit bone resorption and prevent the onset of osteoporosis, and the weak estrogenic effects of isoflavones have been postulated as being protective against various forms of cancer.