THE EFFECT OF CALCIUM GLUCONATE AND OTHER CALCIUM SUPPLEMENTS AS A DIETARY CALCIUM SOURCE ON MAGNESIUM ABSORPTION IN RATS

The effects of commercially available calcium supplements (calcium car bonate, calcium gluconate, oyster shell preparation and bovine bone pr eparation) and gluconic acid on the absorption of calcium and magnesiu m were evaluated for 30 days in male Wistar rats. There were no differ ences in the apparent absorption ratio of calcium among rats fed each calcium supplement; however the rats fed the calcium gluconate diet ha d a higher apparent absorption ratio of magnesium than the rats fed th e other calcium supplements. Dietary gluconic acid also more markedly stimulated magnesium absorption than the calcium carbonate diet, and t he bone (femur and tibial magnesium contents of rats fed the gluconic acid diet were significantly higher than those of the rats fed the cal cium carbonate diet. Furthermore, the weight of cecal tissue and the c oncentrations of acetic acid and butyric acid in cecal digesta of rats fed the calcium gluconate diet or the gluconic acid diet were signifi cantly increased. We speculate that the stimulation of magnesium absor ption in rats fed the calcium gluconate diet is a result of the glucon ic acid component and the effect of gluconic acid on magnesium absorpt ion probably results from cecal hypertrophy, magnesium solubility in t he large intestine and the effects of volatile fatty acids on magnesiu m absorption.