Inclusion of 95 % range in the model to account for inter-individual variability increased the predicted intake of vitamin D needed to maintain serum 25(OH)D ≥ 50 nmol/l to 930 IU/d .
Estimation of the dietary requirement for vitamin D in healthy adolescent white girls.
BACKGROUND Knowledge gaps have contributed to considerable variation ( between 0 and 15 μg/d ) in international dietary recommendations for  vitamin D in adolescents . OBJECTIVE We aim ed to establish the distribution of dietary vitamin D required to maintain serum 25-hydroxyvitamin D [ 25(OH)D ] concentrations above several proposed cutoffs ( 25 , 37.5 , 40 , and 50 nmol/L ) during wintertime in adolescent white girls . DESIGN Data ( baseline and 6 mo ) from 2 r and omized ,  placebo-controlled  , double-blind , 12-mo intervention studies in Danish ( 55 ° N ) and Finnish ( 60 ° N ) girls ( n = 144 ; mean age : 11.3 y ; mean vitamin D intake : 3.7 μg/d ) at vitamin D(3 ) supplementation amounts of 0 , 5 , and 10 μg/d were used . Serum 25(OH)D was measured with an HPLC assay in a central ized laboratory . RESULTS Clear dose-related increments ( P < 0.0001 ) in serum 25(OH)D with increasing supplemental vitamin D(3 ) were observed . The slope of the relation between vitamin D intake and serum 25(OH)D at the end of winter was 2.43 nmol ⋅ L(-1 ) ⋅ μg intake(-1 ) , and no difference in the slopes between Finnish and Danish girls was observed . The vitamin D intakes that maintained serum 25(OH)D concentrations at > 25 , > 37.5 , and > 50 nmol/L in 97.5 % of the sample were 8.3 , 13.5 , and 18.6 μg/d , respectively , whereas an intake of 6.3 μg/d maintained a serum 25(OH)D concentration > 40 nmol/L in 50 % of the sample . CONCLUSION The vitamin D intakes required to ensure that adequate vitamin D status [ defined variably as serum 25(OH)D > 25 and > 50 nmol/L ] is maintained during winter in the vast majority ( > 97.5 % ) of adolescent girls ( mean age : 11.3 y ) at northern latitudes ( > 55 ° N ) are 8.3 and 18.6 μg/d , respectively . This trial was registered at clinical trials.gov as NCT00267540
Inclusion of 95 % range in the model to account for inter-individual variability increased the predicted intake of vitamin D needed to maintain serum 25(OH)D ≥ 50 nmol/l to 930 IU/d .