Effect of Protein Intake on Calcium Balance of Young Men Given 500 mg Calcium Daily

The effect of level of protein intake on urinary and fecal calcium and calcium balance of nine young adult human males was investigated. Calcium intake was 500 mg daily and protein intake was varied from 47 to 95 to 142 g daily. When the protein intake was 47 g daily, the mean calcium retention of the subjects was 31 mg, with only two subjects showing a slight negative balance. When the protein intake was 95 and 142 g, respectively, the mean calcium balance was -58 and -120 mg, and no subject was in calcium balance. Increasing the intake of fruits and vegetables by 50% had no beneficial effect on calcium balance. The urinary calcium increased significantly with each increase in protein intake, the mean value being 168, 240, 301 and 278 mg, respectively, when the low, the medium and the high protein and the high protein-high fruit and vegetable diet was given. Fecal calcium was not significantly affected by protein intake.