The relationship between magnesium and calcium kinetics in 9- to 14- year-old children

Abstract

Few measurements of magnesium (Mg) kinetics have been performed, especially in children and adolescents. Simultaneous Mg and calcium (Ca) kinetics following intravenous administration of 42Ca and 25Mg were measured in 22 children (10 boys and 12 girls) 9-14 years of age. Kinetic values, including the body pool masses (Mg(Comp) and Ca(Comp) for the and Ca compartment masses, respectively) and bone/tissue (hard and soft tissue) Ca and Mg deposition rates (V(o) + Ca and V(o)+Mg, respectively) were calculated using the Simulation, Analysis, and Modeling (SAAM) program. No significant differences were found between males and females (p > 0.3 for each comparison) for pool masses or deposition rates. V(o)+Ca and V(o)+Mg were highly correlated (r = 0.78, p < 0.001). V(o)+Mg but not V(o)+Ca, was closely correlated with body weight (r = 0.55, p < 0.01 and r = 0.16, p = 0.47, respectively). Similarly, Mg(Comp) was more closely correlated with body weight (r = 0.76, p < 0.01) than Ca(Comp) (r = 0.37,p = 0.10). Neither V(o)+Ca nor Ca(Comp) increased significantly over the age range studied. However, V(o)+Mg and Mg(Comp) were significantly positively correlated with age. These findings demonstrate differences in regulation of Ca versus Mg kinetics by young adolescents. These differences may be related to the greater utilization of Mg for muscle and soft tissue growth. The close relationship between V(o)+Mg and body weight suggests that the current practice of relating Mg intake requirements to body weight, as well as age, is appropriate for young adolescents.