TABLE 4-3 Factorial Approach for Determining Calcium Requirements During Peak Calcium Accretion in White Adolescents

 

Number of Observations

Females (mg/day)

Number of Observations

Males (mg/day)

Peak calcium accretion

507

212a

471

282a

Urinary losses

28

106b

14

127c

Endogenous fecal calcium

14

112d

3

108e

Sweat losses

 

55f

 

55f

Total

 

485

 

572

Absorption, percent

14

38d

14

38d

As adjusted for absorption

 

1,276

 

1,505

a Martin et al., 1997, using peak bone mineral content velocity.

b Weaver et al., 1995 and Greger et al., 1978.

c Matkovic, 1991.

d Wastney et al., 1996 for mean age 13 years on calcium intakes of 1,330 mg/day.

e Abrams et al., 1992.

f Taken from Peacock (1991) who adjusted the adult data of Charles et al. (1983) for body weight.

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



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