Differential effects of isoflavones on bone formation in growing male and female mice.

Few studies have examined the effects of isoflavones on bone formation during growth period in male and female animals. In this study, the effects of daidzein or genistein on bone formation were assessed in immature male and female mice. Five-week-old male and female mice were divided respectively into 3 groups (n=8 per group) as follows: control group (C) fed a control diet (AIN-93G), daidzein group (D) fed a control diet containing 0.08% pure daidzein, and genistein group (G) fed a control diet containing 0.08% pure genistein. After 4 weeks, the male D group had a significantly higher bone mineral density (BMD) in whole body, lumbar spine, and femur than did the C group. On the contrary, BMD of the whole body and femur in the female D group was significantly lower than that in the C group. The BMD of the whole femur in the male G group also was significantly higher than for the C group. Histologic analysis revealed that the bone formation rate was significantly higher in the male D and G groups, and lower in the female D group compared with the C group. These results suggest that daidzein has a specific, sexually dimorphic effect on bone formation and BMD during growth period in mice.