The effect of phosphorus on endogenous fecal calcium excretion in man.

The effect of phosphorus on the endogenous fecal calcium excretion was investigated in man by administering tracer doses of 47Ca intravenously in control studies and during phosphorus supplementation. The phosphorus intake was approximately 800 mg/day in control studies and 2000 mg during phosphorus supplementation of the constant diet. The studies were carried out during different calcium intake levels of approximately 200, 800, 1300, 2000, and 2600 mg/day. Following the dose of 47CaCl2, the values of the plasma levels, urinary, and fecal excretions of 47Ca were used to calculate the endogenous fecal calcium. None of these values differed significantly during phosphorus supplementation from those in corresponding control studies, irrespective of the calcium intake. During addition of phosphorus to the different calcium intakes, a consistent finding was a significant decrease of the urinary calcium and a slight, but not significant increase of the fecal calcium except during the 800 mg calcium intake.