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.