CALCIURIC EFFECTS OF PROTEIN AND POTASSIUM BICARBONATE BUT NOT OF SODIUM-CHLORIDE OR PHOSPHATE CAN BE DETECTED ACUTELY IN ADULT WOMEN AND MEN

An acute load test was used to test the influence of dietary factors o n urinary calcium excretion. In study 1, 10 fasting premenopausal wome n consumed test meals providing a moderate amount of protein (MP; 23 g ), MP plus 23 mmol KHCO3 (MP + K), MP plus 23 mmol NaCl (MP + Na), and a high amount of protein (HP; 53 g), HP plus 70 mmol KHCO3 (HP + K), and HP plus 70 mmol NaCl (HP + Na). Protein was casein:lactalbumin (80 :20), except for the treatments with added sodium chloride, to which o nly casein was added. In study 2, the effects of HP and HP plus 50 mmo l KHCO3 (HP + K) were compared with those of MP or MP plus 7.5 mmol ph osphate (MP + Pi), equaling the additional phosphate of HP, in 10 adul t men. Subjects completed all treatments in random order. In study 1, the peak of calcium excretion was at 3 h for all treatments, except fo r HP + K, which indicated an acute hypocalciuric effect of potassium. Unexpectedly, there was no hypercalciuric effect of adding sodium chlo ride, nor was urine sodium increased. In study 2, calcium excretion wa s significantly higher with HP than with MP + Pi but not with MP at 3 h, indicating an acute hypercalciuric effect of protein alone. A hypoc alciuric effect of potassium (HP + K compared with HP) but not of phos phate (MP compared with MP + Pi) was seen. An acute load test measurin g changes 3 h postload was appropriate for examining the calciuric eff ects of protein and potassium bicarbonate, but not those of sodium chl oride or phosphate in adults.