EFFECT OF MILK PROTEIN, SODIUM CHLORIDE, AND POTASSIUM CITRATE ON ACUTE URINARY CALCIUM EXCRETION IN CHILDREN
Date
1996-03
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ORCID
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Degree Level
Masters
Abstract
Studies using adult human subjects indicate that dietary protein and sodium chloride can have a negative impact on the retention of calcium by increasing urinary calcium excretion. Conversely, alkaline potassium can improve calcium retention by decreasing urinary calcium losses. Childhood is an important time for bone growth, however, the effect of these dietary
factors on calcium metabolism in children has not been addressed.
This study investigated the effects of oral potassium citrate (K-citrate), sodium chloride (NaCl), and milk protein on short-term urinary calcium excretion in 6-10 year old girls. Subjects provided a fasting urine sample then consumed a base meal and one of five supplements: 8.6 g protein (MP); 8.6 g protein + 25.7 mmol sodium chloride (MP+Na); 25.6 g protein (HP); 25.6 g
protein + 25.7 mmol sodium chloride (HP+Na); or 25.6 g protein + 10.8 mmol tri-potassium citrate (HP+K). Urine was collected at 1.5 and 3.0 hours after the meal. Fourteen healthy Caucasian girls ages 6.7-10.0 years old completed all treatments, with at least 48 hours between each test. Supplemental protein was 80% casein and 20% lactalbumin, to simulate cow's milk protein, and contained 0.2 mmol phosphorus per gram. Results were statistically analyzed by Repeated Measures ANOVA and Student-Newman-Keels test.
Urinary calcium excretion rose after the meal, peaking at 1.5 hours after all treatments. There were no significant differences in calcium excretion between treatments at any time point. HP, which did not increase urinary calcium excretion compared to MP, also did not result in an increase in either net acid or sulfate excretion at 1.5 hours. Dietary sodium chloride had no effect on urinary sodium or calcium excretion over the three hours. However, fasting calcium excretion (mmol/mmol creatinine) was correlated with fasting sodium excretion (mmol/mmol creatinine) (r=0.53, p<0.001) for the 70 fasting samples collected during the study. Urinary potassium excretion was increased at 1.5 and 3 hours with HP+K (p<0.001). Also, at 1.5 hours after the HP+K treatment, sodium and phosphate excretion were increased (p≤0.002) and net acid excretion was decreased (p<0.001).
The results of this study indicate that in children, a simultaneous increase in protein and phosphorus due to increased milk protein intake does not increase acute urinary calcium excretion. There was no effect of a sodium chloride load on urinary calcium excretion seen within the short time-frame of this model. These findings are similar to those of adult studies conducted in the same laboratory using a similar format and treatments. To study the effect of dietary sodium chloride on urinary calcium excretion, longer time periods are necessary. The observation that potassium citrate is not hypocalciuric in children differs from that for adults, who show a decrease in urinary calcium excretion in response to a load of alkaline potassium. The physiological responses of children to dietary factors are not necessarily the same as those of adults. Further research needs to be conducted to determine appropriate dietary recommendations which maximize bone mass in children.
Description
Keywords
urinary calcium excretion
Citation
Degree
Master of Science (M.Sc.)
Department
Pharmacy and Nutrition