Mineral utilization by rats fed various commercially available calcium supplements or milk

The effects of commercially available calcium supplements and milk on tissue levels and apparent absorption of calcium, magnesium, phosphorus, zinc, iron and copper were evaluated in two studies with rats. Calcium supplements (calcium phosphate dibasic, oyster shell preparations with and without supplemental magnesium, calcium lactate, calcium carbonate with and without supplemental iron and vitamins, dolomite and chelated calcium with and without chelated magnesium) and nonfat dry milk were the sole sources of calcium in nutritionally adequate diets. Rats fed calcium phosphate dibasic had enlarged kidneys with greater than 20-fold increases in calcium levels. The rats fed the three magnesium-fortified supplements had lower apparent absorption of calcium and iron and less accumulation of calcium in bone than rats fed milk. There were few differences in the utilization of calcium by rats fed milk or supplements containing only calcium lactate, chelated calcium, oyster shells and calcium carbonate, but magnesium retention in bone was greater among rats fed milk.