Abstract
Several beneficial effects of soy protein were claimed for the prevention of heart disease and osteoporosis. These effects may be mediated through the soy isoflavones, which are known to bind the estrogen receptor. We performed a study in early postmenopausal women of the effect of soy protein with two levels of isoflavones; 65 women, mean age 55 y, were randomly assigned to one of three groups in a double-blind study--Group A received soy with 96 mg, Group B received soy with 52 mg isoflavones and Group C received soy protein without isoflavones. Treatment was given for 9 mo. Bone mineral density (BMD) was measured at baseline and after 9 mo. The results showed no effect of any of the supplemented soy compounds on spine or femur BMD (Table 1). There were no significant differences among the three groups in spine, femoral neck or trochanter BMD during the intervention phase. Measurement of serum isoflavones at 3 mo showed dose-related increases in the two supplemented groups; in the 96-mg group, the serum isoflavones were 10 times greater than those in the nonsupplemented group. In summary, soy supplemented with 52 and 96 mg of isoflavones had no effect on spine or femur BMD, suggesting that this level of isoflavones is ineffective in the prevention of early postmenopausal bone loss.