The influence of dietary calcium on kidney calcification and renal function in rats fed high-phosphate diets.

This study was carried out to test the hypothesis that kidney calcification caused by high dietary phosphorus intake can be prevented by increasing the calcium content of the diet, because the latter reduces the intestinal P absorption. The investigation was conducted in rats fed semipurified diets with either a low (0.15%) or a high (1.20%) P content. Although dietary Ca supplementation (as CaCO3 or CaCl2) reduced the intestinal P absorption, it did not prevent kidney calcification induced by high dietary P. On the contrary, when CaCO3 was supplemented for 16 weeks, renal calcification increased, probably due to the alkaline nature of this salt. Both CaCO3 and CaCl2 in the high-P diets adversely influenced Mg use. This might explain the failure of these salts to prevent kidney calcification.