Effects of a variety of calcium sources on mineral metabolism in anemic rats.

The effects of commercially available calcium supplements (calcium carbonate, oyster shell, chelated calcium and magnesium, calcium phosphate dibasic) and milk on tissue levels and apparent absorption of calcium, magnesium, phosphorus, iron, zinc, and copper were evaluated with rats that had been made anemic by dietary iron depletion. Hematocrits of anemic rats fed the chelated calcium and magnesium were restored more slowly than rats fed the other calcium sources. The rats fed chelated calcium and magnesium also retained less iron in their livers than rats fed calcium phosphate dibasic, oyster shells, or calcium carbonate and retained less calcium in bone than rats fed milk, oyster shells, or calcium phosphate dibasic. Rats fed calcium phosphate dibasic had on average 40-fold higher levels of calcium in their kidneys than rats fed the other diets. The molar ratio of additional calcium and phosphorus in kidneys of these rats was 3:2.