A double-blind, placebo-controlled study involving over 200 postmenopausal Chinese women suggests that soy isoflavones can help women with low bone mineral content prevent hip fractures in postmenopause years. The trial, reported in the Journal of Clinical Endocrinology and Metabolism, randomly divided women into three treatment groups which received daily either a placebo, a medium dose of isoflavones (40 mg isoflavones) or a high isoflavone dose (80 mg isoflavones). All three groups were also given 500 mg of calcium and 125 IU vitamin D daily. At the beginning of the study and one year later, researchers measured bone mineral density (BMD) and bone mineral content (BMC) of the whole body, spine and hip.
Women receiving the high dose of isoflavones had mild, but a significantly higher improvement in BMC at the total hip and trochanter compared to those in the placebo and mid-dose groups, even after adjustments for potential confounding factors. Further analyses revealed that soy isoflavone supplementation was only beneficial among women who started out with average or lower bone mineral content measurements. The researchers concluded, ¡°¡­ soy isoflavones have a mild, but significant, independent effect on the maintenance of hip BMC in postmenopausal women with low initial bone mass,¡±¡ªin other words, soy isoflavones improve bone density in women who need it, while having little effect on the bones of those whose bone density is already adequate.
The results of this study provide additional support for the findings of a review study published in the American Journal of Clinical Nutrition. In their review, Drs. Kenneth Setchell, one of the foremost researchers in soy¡¯s effects on health, and Eva Lydeking-Olsen examined 17 in vitro studies of cultured bone cells, 24 in vivo animal models for postmenopausal osteoporosis, 15 human observational/epidemiologic studies, and 17 dietary intervention studies. Their conclusions: ¡°the collective data suggest that diets rich in phytoestrogens have bone-sparing effects in the long term, although the magnitude of the effect and the exact mechanism(s) of action are presently elusive or speculative."