^a From NRC (1989). Details of the studies cited are given in Table 4-4.

^b SD = Standard deviation.

^c Standard deviation not applicable to RDA.

^d NR = Not reported.

^e Standard error of the mean.

^f Units are IU; 1 µg vitamin D = 40 IU.

^g Reported standard deviation is not included because of a suspected error.

^h Unsupplemented women.