Role of the sulfur-containing amino acids in protein-induced hypercalciuria in men

A human metabolic study was conducted to determine what part sulfur-containing amino acids play in protein-induced hypercalciuria. The effects on the renal handling of calcium of increasing dietary protein from 50 to 150 g protein were compared with those of increasing the sulfur amino acids to simulate the amounts present in the 150 g protein diet; we also evaluated the effects of adding a 1.5 g supplement of phosphorus to the 50 g protein diet containing the sulfur amino acids. An increase in protein intake caused urinary calcium to double, increased glomerular filtration rate and decreased fractional renal tubular reabsorption of calcium and urinary sodium. Sulfur amino acids added to the low protein diet also caused urinary calcium to increase and fractional tubular reabsorption of calcium and urinary sodium to decrease, but the changes were only 43, 44 and 66%, respectively, those caused by the increase in protein. The phosphorus supplement effectively prevented the hypercalciuria caused by adding the sulfur amino acids to the low protein diet.