Sj. Whiting et al., EFFECTS OF EXCESS PROTEIN, SODIUM AND POTASSIUM ON ACUTE AND CHRONIC URINARY CALCIUM EXCRETION IN YOUNG-WOMEN, Nutrition research, 18(3), 1998, pp. 475-487
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.