Retention of bone strength by feeding of milk and dairy products in ovariectomized rats: involvement of changes in serum levels of 1alpha, 25(OH)2D3 and FGF23.

The current study compared the effects of milk, yogurt or whey on the bone strength, body composition and serum biomarkers. Forty 12-week-old female Sprague-Dawley rats were ovariectomized (OVX), and another nine rats received a sham operation (Sham-Cont). After a 1-week recovery period, the OVX rats were divided into four dietary groups: OVX-control group (OVX-Cont), 17% skimmed milk powder diet group (OVX-Milk), 17% powdered fermented milk diet group (OVX-Yogurt) and 12% whey powder and 6% whey protein extract diet group (OVX-Whey) (n=10 in each group). The protein, nitrogen, fat, calcium and phosphorus contents of the experimental diets were adjusted to be similar to the control diet (AIN-93M). Eighty-four days after the beginning of the experimental diet, the total bone mineral density and bone mineral contents of lumbar vertebrae were significantly higher in the OVX-Milk and OVX-Whey groups than in the OVX-Cont group. Furthermore, the level of 1alpha, 25-dihydroxyvitamin D3 [1alpha, 25(OH)2D3] was significantly lower, while the serum level of FGF23 was significantly higher in the OVX-Milk, OVX-Yogurt and OVX-Whey groups than in the OVX-Cont group. These findings suggest that milk and the dairy products could improve bone metabolism in a postmenopausal animal model at least partly through changing the balance between 1alpha, 25(OH)2D3 and FGF23.