title: The impact of 1-year vitamin D supplementation on vitamin D status in athletes: a dose-response study.
abstract: To assess the prevalence of vitamin D deficiency in Dutch athletes and to define the required dosage of vitamin D3 supplementation to prevent vitamin D deficiency over the course of a year.
  
  
  
  Blood samples were collected from 128 highly trained athletes to assess total 25(OH)D concentration. Of these 128 athletes, 54 male and 48 female athletes (18-32 years) were included in a randomized, double blind, dose-response study. Athletes with either a deficient (<50 nmol/l) or an insufficient (50-75 nmol/l) 25(OH)D concentration were randomly assigned to take 400, 1100 or 2200 IU vitamin D3 per day orally for 1 year. Athletes who had a total 25(OH)D concentration above 75 nmol/l at baseline continued with the study protocol without receiving vitamin D supplements. Serum total 25(OH)D concentration was assessed every 3 months, as well as dietary vitamin D intake and sunlight exposure.
  
  
  
  Nearly 70% of all athletes showed an insufficient (50-75 nmol/l) or a deficient (<50 nmol/l) 25(OH)D concentration at baseline. After 12 months, serum 25(OH)D concentration had increased more in the 2200 IU/day group (+50±27 nmol/l) than the sufficient group receiving no supplements (+4±17 nmol/l; P<0.01) and the 1100 IU/day group (+25±23 nmol/l; P<0.05). Supplementation with 2200 IU/day vitamin D resulted in a sufficient 25(OH)D concentration in 80% of the athletes after 12 months.
  
  
  
  Vitamin D deficiency is highly prevalent in athletes. Athletes with a deficient or an insufficient 25(OH)D concentration can achieve a sufficient 25(OH)D concentration within 3 months by taking 2200 IU/day.
authors.affiliation: Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.
authors.forename: E M P
authors.initials: EM
authors.lastname: Backx
authors.affiliation: Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Tieland
authors.affiliation: Netherlands Olympic Committee*Netherlands Sports Confederation (NOC*NSF), Arnhem, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Maase
authors.affiliation: DSM Biotechnology Center, Delft, The Netherlands.
authors.forename: A K
authors.initials: AK
authors.lastname: Kies
authors.affiliation: Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Mensink
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands.
authors.forename: L J C
authors.initials: LJ
authors.lastname: van Loon
authors.affiliation: Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.
authors.forename: L C P G M
authors.initials: LC
authors.lastname: de Groot
mesh_terms: D000293:Adolescent; D000328:Adult; D056352:Athletes; D002762:Cholecalciferol / Q000097:blood / Q000494:pharmacology / Q000627:therapeutic use*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D009426:Netherlands; D013178:Sports Medicine; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000188:drug therapy*; D055815:Young Adult
chemical_list: D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D