Effect of calcium on phosphorus metabolism in man

The effect of calcium on phosphorus metabolism was studied in adult males by determining phosphorus and calcium balances during three calcium intakes of approximately 200, 800, and 2000 mg/day. Each of these calcium intakes were given during two intake levels of phosphorus of approximately 800 and 2000 mg/day. In all studies, the addition of different amounts of calcium led to a significant decrease of the urinary phosphorus, a significant increase of the stool phosphorus, and significant improvement of the phosphorus balance irrespective of the phosphorus intake. Only in one study in which the calcium intake was increased from 230 to 831 mg/day during the high phosphorus intake of approximately 2000 mg/day were these changes not significant. During all calcium intakes, the decrease in urinary phosphorus was greater than the increase in stool phosphorus irrespective of the phosphorus intake. The apparent absorption of phosphorus decreased on increasing the calcium intake. The calcium balance was not adversely affected by increasing the phosphorus intake to 2000 mg/day during any of the calcium intakes.