CALCIUM AND MAGNESIUM BALANCE IN 9-14-Y-OLD CHILDREN

Few data are available regarding calcium and magnesium absorption and endogenous fecal excretion in children. We used a multitracer stable i sotope technique to assess calcium and magnesium balance in 12 boys an d 13 girls aged 9-14 y (mean weight: 42 kg) maintained on relatively h igh calcium intakes (mean: 1310 +/- 82 mg/d). There were no significan t differences in absorption of calcium or magnesium from milk between boys and girls. Calcium retention (balance) correlated positively with calcidiol (25-hydroxyvitamin D) concentration (r = 0.48, P = 0.02) an d serum alkaline phosphatase activity (r = 0.44, P = 0.03). There was no significant relation between magnesium balance and concentration. W hen data from this study were combined with our previously reported da ta, an increase in total calcium absorption was seen for pubertal (Tan ner stages 2-4) but not prepubertal (Tanner stage 1) white children ov er the range of intakes from approximate to 750 to 1350 mg/d. Despite intakes similar to the 1989 recommended dietary allowance for magnesiu m (mean intake: 6.4 +/- 1.2 mg . kg(-1) . d(-1)), 11 of the 25 subject s (6 girls and 5 boys) were in negative magnesium balance. We conclude that benefits from higher calcium intakes, less than or equal to 1350 mg/d, were most apparent in pubertal children. In addition, higher ma gnesium intakes should be considered for children.