of 50 nmol/L and above. This is consistent with conclusions inferred from calcium absorption studies and, in turn, with the ability to cover the requirements for nearly all in the population. A relatively wide range of total vitamin D intakes reportedly achieved serum 25OHD concentrations between approximately 40 and 60 nmol/L, but most intakes were between about 350 and 600 IU/day. The variability in the data cannot be readily attributed to differences in sun exposure because the studies were all conducted in northern locations during primarily winter months.

Taken as a body of evidence and in the absence of measures that directly relate total intake to health outcomes, the information concerning serum 25OHD concentrations associated with rickets prevention, calcium absorption, and positive effects on BMC measures are consistent with discussions above concerning a requirement distribution based on serum 25OHD concentrations. They support the conclusion that an average requirement for vitamin D for these life stage groups is associated with the achievement of concentrations of 25OHD in serum of 40 nmol/L. Further, they support the conclusion that the requirements for nearly all children and adolescents are covered when serum 25OHD concentrations reach 50 nmol/L. These findings are universally applicable across all children and adolescents from 1 to 18 years of age.

The analysis conducted, described above, indicates that an intake of vitamin D of 400 IU/day achieves serum concentrations of 40 nmol/L, and this intake is therefore set as the EAR for persons 1 to 3 years, 4 to 8 years, 9 to 13 years, and 14 to 18 years of age. As this requirement distribution appears to be normally distributed, the assumption of another 30 percent to cover nearly all the population (i.e., 97.5 percent) is appropriate and consistent with a serum 25OHD level of approximately 50 nmol/L as the target for an RDA value. Based on the same analysis relating serum 25OHD levels to intake, an intake of 600 IU/day is set as the RDA. These reference values assume minimal sun exposure.

For these life stage groups, bone maintenance is the focus. The requirement distribution based on serum 25OHD concentrations and the intakes estimated to achieve such concentrations are the basis for the reference values. As described below, the available data have provided more