title: Estimation of the dietary requirement for vitamin D in healthy adolescent white girls.
abstract: 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 aimed 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.
  
  
  METHODS
  Data (baseline and 6 mo) from 2 randomized, 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 centralized 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.
  
  
  CONCLUSIONS
  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 clinicaltrials.gov as NCT00267540.
authors.affiliation: School of Food and Nutritional Sciences, Department of Medicine, University College Cork, Cork, Ireland. k.cashman@ucc.ie
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Cashman
authors.forename: Anthony P
authors.initials: AP
authors.lastname: FitzGerald
authors.forename: Heli T
authors.initials: HT
authors.lastname: Viljakainen
authors.forename: Jette
authors.initials: J
authors.lastname: Jakobsen
authors.forename: Kim F
authors.initials: KF
authors.lastname: Michaelsen
authors.forename: Christel
authors.initials: C
authors.lastname: Lamberg-Allardt
authors.forename: Christian
authors.initials: C
authors.lastname: Mølgaard
mesh_terms: D000293:Adolescent; D002112:Calcifediol / Q000097:blood; D002648:Child; D002762:Cholecalciferol / Q000008:administration & dosage*; D003718:Denmark; D004032:Diet; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005387:Finland; D006801:Humans; D008954:Models, Biological; D018673:Nutrition Policy; D009751:Nutritional Requirements; D009752:Nutritional Status; D012621:Seasons; D011795:Surveys and Questionnaires; D014808:Vitamin D Deficiency / Q000097:blood / Q000517:prevention & control*; D044465:White People
chemical_list: D002762:Cholecalciferol; D002112:Calcifediol