Comparative effects of milk and soymilk on bone loss in adult ovariectomized osteoporosis rat

The present study was designed to investigate the comparative effects of milk and soymilk on the bone morphology of ovariectomized rat model with postmenopausal osteoporosis. Fourty 12-week-old female Spraque-Dawley rats were randomly divided into the following 5 groups: intact control (control), sham-operated (sham), ovariectomized (OVX), ovariectomized and fed milk (milk), ovariectomized and fed soymilk (soymilk) groups. Rats of OVX, milk and soymilk groups were bilaterally ovariectomized. Milk or soymilk of 3 ml was administered by gavage via an intragastric tube per day for 6 weeks. The distal femoral metaphysis was studied morphologically, together with bone mineral density (BMD), serum parathyroid hormone (PTH) and estradiol levels. In the OVX group, the trabecular bone volume was significantly reduced. The percentage area of resorbing surface was high. In the soymilk group, the trabecular bone volume was 68% higher and the percentage area of resorbing surface was 18% lower as compared with the OVX group. The serum estradiol level rose 48% and the serum PTH level fell 26% in the soymilk group. In the milk group, the trabecular bone volume had the tendency to be high, but there was no significant change of the bone morphology. The present study provides certain evidence that the soymilk has beneficial effects in preventing bone loss in rats induced by ovarian hormone deficiency.