Effect of estrogenic compounds (estrogen or phytoestrogens) combined with exercise on bone and muscle mass in older individuals.

Exercise has a beneficial effect on bone, possibly by stimulating estrogen receptor alpha. Because estrogen up-regulates this receptor, estrogen therapy combined with exercise training may be optimal for increasing bone mineral density. Studies combining estrogen therapy and exercise training in postmenopausal women show mixed results, but indicate that the combination of interventions may be more effective for increasing bone mass than either intervention alone. Plant-like estrogens (i.e phytoestrogens such as soy isoflavones) may act as weak estrogen agonists or antagonists, have small beneficial effects on bone, and may interact with exercise for increasing bone mineral density. Phytoestrogen derived from flaxseed (flax lignans) has not been evaluated as extensively as soy isoflavones and thus its effect on bone is difficult to determine. Estrogen or soy isoflavones given to postmenopausal women results in a small increase in lean tissue mass that may be mediated through estrogen receptor alpha on muscle or through decreased inflammation.