Phosphate supplementation in young men: lack of effect on calcium homeostasis and bone turnover

Objective: To examine the effect of phosphate supplements on calcium homeostasis and bone turnover in young men. Design: Study 1 was a randomised, controlled, cross-over trial of 1000 mg elemental phosphate given for one week, with a standard diet of 800 mg/d each of calcium and phosphorus. Study 2 was an escalating dose study of 0, 1000, 1500 and 2000 mg/d elemental phosphate, each given for one week, with a standard diet of 1000 mg/d each of calcium and phosphate. Setting: Northern General Hospital, Sheffield. Subjects: Study 1, 10 healthy men ages 19-32 y. Study 2, 12 healthy men ages 19-38 y. Interventions: Sodium acid phosphate tablets each containing 500 mg elemental phosphorus (16.1 mmol/d), given with meals. Results: Study 1, administration of 32.2 mmol/d phosphorus resulted in a mean increase of 13.2 mmol/d urinary phosphorus, a mean decrease of 1.1 mmol/d urinary calcium, and a mean increase of 7 ng/mL in serum intact PTH. There were no changes in serum phosphate, osteocalcin or urinary N-telopeptide excretion. Study 2, administration of 64.4 mmol/d phosphorus resulted in a mean increase of 27.2 mmol/d urinary phosphorus, a mean decrease of 2.4 mmol/d urinary calcium, with no change in serum phosphate, PTH or urinary deoxypyridinoline. Conclusions: Phosphate supplementation of the diet does not affect bone turnover in young men.