were hindered because of no reported randomized clinical trials testing multiple intakes of calcium, the lack of data on whole body bone mineral accretion, and the uncertainties in the values for endogenous fecal and sweat losses of calcium used in the factorial model. Thus, the estimate for the AI relies on using available calcium balance studies to determine intakes at which small gains in bone mineral content can be achieved. Because of the uncertainties related to the five-fold difference in estimated bone calcium accretion between genders during this time period, and the fact that the balance data are predominantly from women, the estimate of calcium intake from the calcium retention analysis for women was adopted for both genders. The estimate of an AI of 1,000 mg (25 mmol)/day was judged to be appropriate for this age group.

Based on desirable calcium retention data and with consideration of the estimates of calcium need from various methods, the AI requirement for both men and women ages 19 through 30 years is set at 1,000 mg (25 mmol)/day.

AI for Men

19 through 30 years

1,000 mg (25 mmol)/day

AI for Women

19 through 30 years

1,000 mg (25 mmol)/day

Adjusting the 1994 CSFII data for day-to-day variation (Nusser et al., 1996), the median calcium intake for men aged 19 through 30 years is 954 mg (23.9 mmol)/day (see Appendix D), which is fairly close to the AI of 1,000 mg (25 mmol)/day for this age group. For women in this age range, the median calcium intake is 612 mg (15.3 mmol)/day, while the ninetieth percentile of intake is 985 mg (24.6 mmol)/day. Thus, an AI of 1,000 mg (25 mmol)/day is slightly above the ninetieth percentile of calcium intake based on the 1994 CSFII data.

Ages 31 through 50 Years
Indicators Used to Set the AI

Calcium Retention. For this age group, as for the others, balance studies were examined to identify the intake associated with a desirable calcium retention —the plateau intake, that at which there is no net loss of calcium. Two balance studies are available that examined estrogen-replete women on their usual calcium intakes (Heaney et al., 1978; Ohlson et al., 1952). Calcium balance was estimated in 25 women aged 30 to 39, with a mean calcium intake of 950 ± 300 mg (23.7 ± 7.5 mmol)/day and 34 women aged 40 to



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