tin et al., 1997). The mean fractional absorption value of 38 percent was based on a study of girls, aged 13 ± 1 years, who consumed an average of 1,330 mg (33.3 mmol)/day of calcium (Wastney et al., 1996). It is unknown whether there are gender differences in absorption in this age range. The values for endogenous excretion and absorption in males in Table 4-3 are based on very few data points, and the values for sweat losses are extrapolated from adult data. Variability about these estimates is large. The values derived from the factorial approach are slightly higher than those obtained using the calcium retention model, but fall within the range of these values and those derived from the clinical trials described above. Because of the extrapolation of values from studies in girls to boys and from adults used in this approach, it was deemed inappropriate to use these values as a basis for an EAR.

Epidemiological Evidence. Several cross-sectional studies have identified a positive association between calcium consumption and bone density in children (Chan, 1991; Ruiz et al., 1995; Sentipal et al., 1991), whereas others have found no such association (Grimston et al., 1992; Katzman et al., 1991; Kröger et al., 1992, 1993). The studies showing the positive association tended to include a significant proportion of study subjects with low calcium intakes. A study