Calcium absorption and kinetics are similar in 7- and 8-year-old Mexican-American and Caucasian girls despite hormonal differences

To assess the possibility of ethnic differences in mineral metabolism in pr epubertal children, we compared measures of calcium metabolism in 7- and 8- y-old Mexican-American (MA) and non-Hispanic Caucasian (CAU) girls (n = 38) living in southeastern Texas. We found similar fractional calcium absorpti on, urinary calcium excretion, calcium kinetic values and total-body bone m ineral content in the MA and CAU girls. In contrast, parathyroid hormone (P TH) concentrations were greater in MA girls (4.01 +/- 0.47 vs. 1.96 +/- 0.5 0 pmol/L, P = 0.005) than in CAU girls. Serum 25-hydroxyvitamin D concentra tions were lower in MA girls (68.9 +/- 7.1 vs. 109.4 +/- 8.4 nmol/L, P = 0. 001) than in CAU girls, but 1,25-dihydroxyvitamin D concentrations did not differ between groups. Seasonal variability was seen for 25-hydroxyvitamin D concentrations in girls of both ethnic groups, but values in all of the g irls were >30 nmol/L (12 ng/mL). We conclude the following: 1) greater PTH levels in MA girls than CAU girls are present without evidence of Vitamin D deficiency; and 2) differences in 25-hydroxyvitamin D and PTH concentratio ns between MA and CAU girls do not have a large effect on calcium absorptio n, excretion or bone calcium kinetics. These data do not provide evidence f or adjusting dietary recommendations for mineral or vitamin D intake by MA girls.