compared to the control twins. However, the increase in BMD was not sustained in a long-term follow-up study when those receiving supplements returned to their normal diets (Slemenda et al., 1997).
In another intervention study, 162 Chinese children who were 7 years of age with low daily calcium intakes (average 280 mg [7 mmol]) were randomly assigned to receive 300 mg (7.5 mmol)/day of a calcium supplement or placebo (Lee et al., 1994). After 18 months, the supplemented group had a significantly greater gain in BMC at the midshaft radius. In a follow-up study for another 18 months, the benefits of calcium supplementation disappeared after the supplements were withdrawn (Lee et al., 1996). In a similar study, greater increases in lumbar spine BMC were seen in 7-year-old children from Hong Kong with average calcium intakes of 570 mg (14.3 mmol)/day who were randomized to receive 300 mg (7.5 mmol)/day supplement compared with those who received a placebo (Lee et al., 1995).
Taken together, the above studies suggest that further evidence is needed regarding the length of time and level of supplementation necessary before a precise requirement value can be based on supplementation data in prepubertal children. There are no long-term studies in which the effects of supplemental calcium given to children prior to age 9 have been evaluated during adulthood.
For females aged 1 through 8 years, calcium accretion in the range of 60 to 200 mg (1.5 to 5 mmol)/day has been predicted from both indirect estimates based on body weight (Leitch and Aitken, 1959) and direct estimates of bone mineral content using DXA (Ellis et al., 1997). The precise calcium intake needed to achieve such calcium accretion cannot be obtained from available data. From balance studies in the older age group, a calcium intake of 800 to 900 mg (20 to 22.5 mmol)/day would result in mean calcium retention up to 174 mg/day. Thus, for the 4- through 8-year-old age group, the AI for calcium is 800 mg (20 mmol)/day. As there are no balance studies available in boys, the data for girls has to be applied to both sexes.
The primary balance data described above for 4- through 8 year olds do not include adequate data applicable to younger children in the second and third years of life. Therefore, AIs for this period must be estimated from data for other age groups. Net accretion appears to be approximately 100 mg (2.5 mmol)/day during this life stage (Leitch and Aitken, 1959). Therefore, using an estimate