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 adults.
BACKGROUND Knowledge gaps have contributed to considerable variation among international dietary recommendations for vitamin D. 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 ( ie , 25 , 37.5 , 50 , and 80 nmol/L ) during wintertime after adjustment for the effect of summer sunshine exposure and diet . DESIGN A r and omized , placebo-controlled , double-blind 22-wk intervention study was conducted in men and women aged 20 - 40 y ( n = 238 ) by using different supplemental doses ( 0 , 5 , 10 , and 15 microg/d ) of vitamin D(3 ) throughout the winter .  Serum 25(OH)D concentrations were measured by using enzyme-linked immunoassay at baseline ( October 2006 ) and endpoint ( March 2007 ) . RESULTS There were clear dose-related increments ( P < 0.0001 ) in serum 25(OH)D with increasing supplemental vitamin D(3 ) . The slope of the relation between  vitamin D intake and serum 25(OH)D was 1.96 nmol x L(-1 ) x microg(-1 ) intake . The vitamin D intake that maintained serum 25(OH)D concentrations of > 25 nmol/L in 97.5 % of the sample was 8.7 microg/d . This intake ranged from 7.2 microg/d in those who enjoyed sunshine exposure , 8.8 microg/d in those who sometimes had sun exposure , and 12.3 microg/d in those who avoided sunshine . Vitamin D intakes required to maintain serum 25(OH)D concentrations of > 37.5 , > 50 , and > 80 nmol/L in 97.5 % of the sample were 19.9 , 28.0 , and 41.1 microg/d , respectively . CONCLUSION The range of vitamin D intakes required to ensure maintenance of wintertime vitamin D status [ as defined by incremental cutoffs of serum 25(OH)D ] in the vast majority ( > 97.5 % ) of 20 - 40-y-old adults , considering a variety of sun exposure preferences , is between 7.2 and 41.1 microg/d
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 .