Phytoestrogens in the prevention of postmenopausal bone loss.

Postmenopausal osteoporosis is a condition associated with low bone mass resulting from the increased bone resorption that occurs following a decline in estrogen levels. Phytoestrogens are plant-derived compounds that have affinity to the estrogen receptor and are able to act as either estrogen agonists or antagonists. Because of their structural similarity to 17-beta-estradiol, they have been studied extensively for their role in the prevention of postmenopausal bone loss. An extensive number of studies employing different types of isoflavone preparations (including soy foods, soy-enriched foods, and soy isoflavone tablets) have been conducted in a wide range of populations, including Western and Asian women. Although there is considerable variability in study design and duration, study population, type of soy isoflavone employed in the intervention, and study outcomes, the evidence points to a lack of a protective role of soy isoflavones in the prevention of postmenopausal bone loss.