to specific levels of magnesium consumed on either an ideal or actual body weight basis. Future experiments might address requirements in relation to energy needs (Shils and Rude, 1996).
Because of the lack of studies in younger children, the data from children 10 to 15 years old (see Table 6-1) were extrapolated using reference body weights. Interpretation of the available balance data are confounded by the lack of information provided on individual body weights, varying age and weight ranges studied within and between studies, and variations in dietary protein (both in amount and source) and calcium (see “Calcium” and “Protein” below). In reviewing the details of the studies summarized in Table 6-1, it appears that, provided the diet has adequate protein for 9 through 13 year olds, group mean positive magnesium balance in the range of 10 mg (0.41 mmol)/day is achieved at intakes of approximately 5 mg (0.21 mmol)/kg/day. In the recent short-term study using multitracer stable isotope technique to assess magnesium balance in 13 adolescent girls (Abrams et al., 1997), the mean magnesium balance was slightly negative (−0.9 ± 41 mg [0.04 ± 1.7 mmol]/day) at comparatively high levels of average intake (6.4 mg [0.27 mmol]/kg/day of magnesium). Some of this may have been due to the amount of calcium in the diet (1,310 mg [33 mmol]/day); however, another recent study using multitracer stable isotopes (Sojka et al., 1997), did not show a significant difference in magnesium balance with two levels of dietary calcium (see “Calcium ” below).
In the one balance study in which children 7 to 9 years old were evaluated, positive magnesium balance was achieved on daily dietary magnesium intakes that ranged from 121 to 232 mg (5.0 to 9.7 mmol)/day (Schofield and Morrell, 1960); a magnesium intake of 5 mg (0.21 mmol)/kg/day appeared to meet some but not all of the younger children's needs. Taken together with the data on older children, the available balance studies suggest that at a magnesium intake of 5 mg/kg body weight/day, some but not all children would be in magnesium balance. The extent to which this represents 50 percent of children in these age groups and pubertal stages meeting their needs is difficult to predict because of the confounding variables of other dietary components. For establishing the EARs for magnesium for children ages 1 through 3 and 4 through 8, for which balance studies are unavailable, the value of 5 mg/kg/day is adopted.