Effect of 1α-hydroxyvitamin D₃ and egg-shell calcium on bone metabolism in ovariectomized osteoporotic model rats

Abstract

Egg-shell calcium (Ca) is one of the effective Ca sources for bone metabolism. In the present study, we investigated whether egg-shell Ca had similar effects compared with calcium carbonate (CaCO₃) when vitamin D₃ (1α(OH)D₃) treatment was given to an osteopo-rotic rat model. In both 1α(OH)D₃-supplemented and -unsupplemented rats, the bone mineral density (BMD) of the lumber spine in the vitamin-supplemented group increased significantly compared with the unsupplemented group. In a Ca balance study, there were also significant differences in intestinal Ca absorption, urinary Ca and fecal Ca between the vitamin-supplemented and -unsupplemented groups. These results show that egg-shell Ca could have similar effects to CaCO₃ on bone metabolism. In contrast with CaCO₃, vitamin D₃ supplementation did not significantly increase serum Ca levels in the egg-shell Ca group; however, the mechanism of Ca absorption is still unclear. Our results suggest that egg-shell Ca may be an effective nutrient in Ca metabolism for people treated with vitamin D₃.