plied are for girls aged 11 through 14 years, and all data are from Caucasians. For this report the nonlinear regression equation was derived by combining the optimally designed calcium balance studies of Jackman et al. (1997), Matkovic et al. (1990), and Greger et al. (1978) which represented 80 children aged 12 through 15 years. The measurements were made over the last 2 weeks of a 3-week balance study in girls consuming calcium intakes of 823 to 2,164 mg (20.6 to 54.1 mmol)/day. The retention of calcium was not corrected for sweat or skins losses of calcium in these studies.

The non-linear regression equation was solved to determine the calcium intake required to achieve a desirable retention of calcium of 282 mg (7.1 mmol)/day for boys and 212 mg (5.3 mmol)/day for girls based on peak whole body bone mineral accretion during adolescence (Figure E-1). The value used for sweat losses of 55 mg (1.4 mmol)/day (Peacock, 1991) was added to the desired retention value since these losses had not been accounted for in the calcium retention studies. The estimate of calcium intake that would result in a desirable level of retention was 1,070 mg (26.8 mmol)/day for females and 1,310 mg (32.8 mmol)/day for males. At this time there are insufficient data to subdivide the age range of 9 through 18 years for either bone mineral accretion or balance measures.

The approach used in this review results in a value which is mid-way between two other estimates of the calcium intake necessary to achieve a plateau balance. In applying a two-component split, linear regression model to balance studies published between 1922 and 1992, Matkovic and Heaney (1992) identified a plateau calcium intake of approximately 1,480 mg (37 mmol)/day during growth. Using the nonlinear regression model (Jackman et al., 1997) on the same data set of reported balances as was used by Matkovic and Heaney (1992) resulted in a lower plateau estimate of 820 mg (20.5 mmol)/day of calcium. It should be noted that included in this historical data set were balances which were measured in children who were not yet equilibrated to the study intake. For the analysis conducted for this report, data were included from published studies only if an adaptation period of at least 2 weeks had occurred before the balance period. Thus, the current recommendation is thought to be a more rigorous analysis of the data available.

Clinical Trials Measuring Bone Mineral Content. Several randomized trials have been conducted in children through adolescence which provide evidence that increasing dietary intakes of calcium of girls above their habitual intake of about 900 mg (22.5 mmol)/day is



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