Soy isoflavones and their bone protective effects.

Several observational studies have suggested that populations with a high dietary soy intake have a lower incidence of osteoporosis-related fractures when compared to Western populations. However, there has not been consistent data to show that soy isoflavones protect against or lessen bone loss. Studies in our laboratory showed that genistein, the major soy isoflavone, could stimulate osteoblastic functions as well as human breast cancer cell growth. These studies raised the concern of whether it would be safe for women who have a prior history of breast cancer to consume soy isoflavone for management of postmenopausal osteoporosis. As increasing the purity of genistein is known to increase its ability to induce human breast cancer cell growth, current effort in our laboratory is to determine if the in vivo bone protective effects will be affected by the complexity of the soy isoflavones extract in ovariectomized mice.