Effects of whey protein on calcium and bone metabolism in ovariectomized rats.

We studied the effects of whey protein (WP) from cow's milk on calcium and bone metabolism in ovariectomized (OVX) rats. Six-week-old female Sprague-Dawley rats were ovariectomized and fed a low-calcium diet (0.03% Ca, 0.3% P) for 4 weeks. The OVX rats were divided into three groups and subjected to two experiments: Exp. 1, Cont group (20% casein, 0.3% Ca), WP (1%) group (19% casein, 1% whey protein, 0.3% Ca) and Low-Ca group (20% casein, 0.03% Ca); and Exp. 2, Cont group (20% casein, 0.3% Ca), WP (1%) group (19% casein, 1% whey protein, 0.3% Ca) and WP (2%) group (18% casein, 2% whey protein, 0.3% Ca). The rats were fed each experimental diet for 4 weeks. The final body weight, weight gain, food intake and food efficiency showed no significant difference between the Cont and WP (1%, 2%) groups in Exps. 1 and 2. There were no significant differences in the calcium balance, serum ALP or serum calcitonin levels between the Cont and WP groups in Exp. 1. But the breaking energies of the WP (1%, 2%) groups were higher than those of the Cont groups in Exps. 1 and 2. As for the amount of calcium, phosphorus and magnesium in the femur, there were no significant differences between the Cont and WP (1%, 2%) groups; however, the amounts of total amino acids in the femur of the WP (1%, 2%) groups were higher than those of the Cont groups in Exps. 1 and 2. The amounts of proline and hydroxyproline in the femur of the WP (1%, 2%) groups were also higher than those of the Cont groups in Exps. 1 and 2. These data indicate that the milk whey protein influence in OVX rats is an increase in bone proteins such as collagen and enhanced bone-breaking energy.