EFFECTS OF EXCESS PROTEIN, SODIUM AND POTASSIUM ON ACUTE AND CHRONIC URINARY CALCIUM EXCRETION IN YOUNG-WOMEN

The extent to which chronic calciuric effects of excess protein, sodiu m and potassium were reflected in fasting and acute urinary excretion was determined in 10 healthy premenopausal women. Chronic excretion wa s measured after one week of stabilization to a high protein (HP) diet by adding 50 g protein (casein and lactalbumin, 80:20) to subjects' u sual diets. Then, randomly, subjects received each of the following tr eatments added to a constant baseline diet in Weeks 2-4: HP, HP + 70 m mol KHCO3 (HP+K), and HP (as casein only) + 70 mmol NaCl (HP+Na). In W eek 5 subjects received the moderate protein (MP) treatment in which 5 0 g carbohydrate was given. Subjects provided 24-hour urine on Days 3 and 4 each week. Fasting blood and urine were obtained the morning of Day 5, after which the acute load study began. Subjects ate meals cont aining one-third (1/3) of the respective treatment, followed by collec tion of timed urine and blood samples. In the chronic load study, calc ium excretion was highest with HP+Na compared to MP and was intermedia te with HP or HP+K treatment. Sodium and potassium excretion were refl ective of the dietary intake. Net acid excretion was lowest when subje cts were given added KHCO,. Sulfate and phosphate excretion were highe st during all of the HP treatments. Fasting sodium and calcium excreti ons were higher after chronic HP+Na or MP treatment compared to HP and HP+K. Acutely, incremental calcium excretion was higher for 1/3HP+Na and also 1/3MP. There was no hypercalciuria due to protein, nor hypoca lciuria due to potassium. There was a modest hypercalciuric effect of sodium chloride. Comparing chronic effects to acute effects in this st udy of acclimated subjects, and to acute effects in unacclimated subje cts from a previous study, similarities were observed. Thus acclimatin g subjects to treatment offers no benefit for studying diet-related ef fects on calcium excretion except to demonstrate a hypercalciuric effe ct of sodium chloride. (C) 1998 Elsevier Science Inc.