DIFFERENCES IN CALCIUM-ABSORPTION AND KINETICS BETWEEN BLACK AND WHITE GIRLS AGED 5-16 YEARS

To assess racial differences in calcium (Ca) metabolism, we measured C a absorption and kinetics in 89 girls (38 black and 51 white) aged 4.9 -16.7 years using a dual-tracer stable isotope technique. We found sig nificantly greater rates of fractional (0.44 +/- 0.13 vs. 0.25 +/- 0.0 8, p < 0.0001) and total calcium absorption (406 +/- 142 vs. 234 +/- 8 2 mg/day, p < 0.0003) in black than in white postmenarcheal girls. Fra ctional absorption of Ca was also greater in black than in white preme narcheal girls (0.39 +/- 0.14 vs. 0.30 +/- 0.10, p = 0.01). Fractional absorption of Ca was more closely correlated to Ca intake in white (r = -0.42, p = 0.002) than in black girls (r = -0.25, p = 0.14). Urinar y Ca excretion was significantly lower in pre- but not postmenarcheal black girls than in white girls. Calcium kinetic values associated wit h bone calcium deposition were greater in black girls, indicating a gr eater rate of bone Ca deposition in both pre- and postmenarcheal black girls. These results suggest that the greater bone mass accumulated d uring childhood and adolescence in black than in white females is due, in part, to greater rates of Ca absorption in black girls.