Racial differences in calcium retention in response to dietary salt in adolescent girls.
BACKGROUND
Sodium is an important determinant of urinary calcium excretion, and race is an important determinant of calcium retention. The effect of dietary sodium on calcium retention and the influence of race have not been studied in adolescence, the life stage during which peak bone mass is accrued.


OBJECTIVE
The study reported here was undertaken to compare racial differences in calcium retention as a function of dietary salt intake.


METHODS
A total of 35 adolescent girls (22 black and 13 white) participated in two 20-d metabolic summer camps, separated by 2 wk, that simulated a free-living environment. The effect of changes in dietary sodium on calcium retention was tested in a randomized-order, crossover design with 2 concentrations of sodium-1.30 g/d (57 mmol/d) and 3.86 g/d (168 mmol/d)-and a constant calcium intake of 815 mg/d (20 mmol/d).


RESULTS
Both race and sodium intake significantly affected calcium retention (P < 0.01). Calcium retention was significantly greater in black girls than in white girls, regardless of dietary sodium intake (P < 0.001). The high-sodium diet significantly reduced calcium retention in both whites and blacks (P < 0.01), primarily through a decrease in net calcium absorption. Black girls excreted significantly less calcium in the urine than did white girls, regardless of diet (P < 0.05).


CONCLUSIONS
Calcium retention is significantly greater in black girls than in white girls but is significantly reduced in girls of both races in response to salt loading.
Wigertz
Karin
K
Departments of Foods and Nutrition and of Statistics, Purdue University, West Lafayette, IN, USA.
Palacios
Cristina
C
Jackman
Lisa A
LA
Martin
Berdine R
BR
McCabe
Linda Doyle
LD
McCabe
George P
GP
Peacock
Munro
M
Pratt
J Howard
JH
Weaver
Connie M
CM
D000293:Adolescent; D044383:Black People; D001842:Bone and Bones / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism* / Q000652:urine; D005260:Female; D006801:Humans; D012982:Sodium, Dietary / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D044465:White People
D012982:Sodium, Dietary; D002118:Calcium