title: Estimation of the dietary requirement for vitamin D in adolescents aged 14-18 y: a dose-response, double-blind, randomized placebo-controlled trial.
abstract: Adolescents are a population group at high risk of low vitamin D status, yet the evidence base for establishing dietary vitamin D requirements remains weak.
  
  
  
  The aim was to establish the distribution of vitamin D intakes required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above proposed cutoffs (25, 30, 40, and 50 nmol/L) during winter in white males and females (14-18 y of age) in the United Kingdom (51°N).
  
  
  
  In a dose-response trial, 110 adolescents (aged 15.9 ± 1.4 y; 43% males) were randomly assigned to receive 0, 10, or 20 μg vitamin D3supplements/d for 20 wk during winter. A nonlinear regression model was fit to total vitamin D intake and postintervention serum 25(OH)D concentrations, and regression-predicted values estimated the vitamin D intakes required to maintain serum 25(OH)D concentrations above specific cutoffs.
  
  
  
  Mean ± SD serum 25(OH)D concentrations increased from 49.2 ± 12.0 to 56.6 ± 12.4 nmol/L and from 51.7 ± 13.4 to 63.9 ± 10.6 nmol/L in the 10- and 20-μg/d groups, respectively, and decreased in the placebo group from 46.8 ± 11.4 to 30.7 ± 8.6 nmol/L (all P ≤ 0.001). Vitamin D intakes required to maintain 25(OH)D concentrations >25 and >30 nmol/L in 97.5% of adolescents were estimated to be 10.1 and 13.1 μg/d, respectively, and 6.6 μg/d to maintain 50% of adolescents at concentrations >40 nmol/L. Because the response of 25(OH)D reached a plateau at 46 nmol/L, there is uncertainty in estimating the vitamin D intake required to maintain 25(OH)D concentrations >50 nmol/L in 97.5% of adolescents, but it exceeded 30 μg/d.
  
  
  
  Vitamin D intakes between 10 and ∼30 μg/d are required by white adolescents during winter to maintain serum 25(OH)D concentrations >25-50 nmol/L, depending on the serum 25(OH)D threshold chosen. This trial was registered at clinicaltrials.gov as NCT02150122 and as International Standard Randomized Controlled Trial Number ISRCTN40736890.
authors.affiliation: Department of Nutritional Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom; t.j.smith@surrey.ac.uk.
authors.forename: Taryn J
authors.identifier: 0000-0001-9543-6461
authors.initials: TJ
authors.lastname: Smith
authors.affiliation: Department of Nutritional Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.
authors.forename: Laura
authors.identifier: 0000-0001-8505-3053
authors.initials: L
authors.lastname: Tripkovic
authors.affiliation: Department of Nutrition, Exercise, and Sports, Faculty of Science, University of Copenhagen, Frederiksberg C, Denmark.
authors.forename: Camilla T
authors.identifier: 0000-0002-5013-0562
authors.initials: CT
authors.lastname: Damsgaard
authors.affiliation: Department of Nutrition, Exercise, and Sports, Faculty of Science, University of Copenhagen, Frederiksberg C, Denmark.
authors.forename: Christian
authors.identifier: 0000-0002-5311-9457
authors.initials: C
authors.lastname: Mølgaard
authors.affiliation: Department of Nutrition, Exercise, and Sports, Faculty of Science, University of Copenhagen, Frederiksberg C, Denmark.
authors.forename: Christian
authors.identifier: 0000-0002-5095-0624
authors.initials: C
authors.lastname: Ritz
authors.affiliation: Department of Nutritional Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.
authors.forename: Saskia L
authors.initials: SL
authors.lastname: Wilson-Barnes
authors.affiliation: Cork Centre for Vitamin D and Nutrition Research, School of Food and Nutritional Sciences.
authors.forename: Kirsten G
authors.initials: KG
authors.lastname: Dowling
authors.affiliation: Cork Centre for Vitamin D and Nutrition Research, School of Food and Nutritional Sciences.
authors.forename: Áine
authors.initials: Á
authors.lastname: Hennessy
authors.affiliation: Cork Centre for Vitamin D and Nutrition Research, School of Food and Nutritional Sciences.|Department of Medicine, and.
authors.forename: Kevin D
authors.identifier: 0000-0002-8185-1039
authors.initials: KD
authors.lastname: Cashman
authors.affiliation: Cork Centre for Vitamin D and Nutrition Research, School of Food and Nutritional Sciences.|Irish Centre for Fetal and Neonatal Translational Research (INFANT), University College Cork, Cork, Ireland.
authors.forename: Mairead
authors.identifier: 0000-0003-0973-808X
authors.initials: M
authors.lastname: Kiely
authors.affiliation: Department of Nutritional Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.
authors.forename: Susan A
authors.identifier: 0000-0003-3153-6345
authors.initials: SA
authors.lastname: Lanham-New
authors.affiliation: Department of Nutritional Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.
authors.forename: Kathryn H
authors.identifier: 0000-0001-7494-9866
authors.initials: KH
authors.lastname: Hart
mesh_terms: D000293:Adolescent; D002118:Calcium / Q000097:blood; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D009751:Nutritional Requirements; D010281:Parathyroid Hormone / Q000097:blood; D012621:Seasons; D013472:Sunlight; D006113:United Kingdom; D014807:Vitamin D / Q000008:administration & dosage* / Q000097:blood*
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; D002118:Calcium
keywords: adolescents; dose-response randomized controlled trial; recommendations; requirements; vitamin D