title: Vitamin D status and supplementation in elite Irish athletes.
abstract: BACKGROUND
  A high prevalence of vitamin D insufficiency/deficiency, which may impact on health and training ability, is evident among athletes worldwide. This observational study investigated the vitamin D status of elite Irish athletes and determined the effect of wintertime supplementation on status.
  
  
  METHODS
  Serum 25-hydroxyvitamin D [25(OH)D], calcium, and plasma parathyroid hormone were analyzed in elite athletes in November 2010 (17 boxers, 33 paralympians) or March 2011 (34 Gaelic Athletic Association [GAA] players). A subset of boxers and paralympians (n = 27) were supplemented during the winter months with either 5,000 IU vitamin D3/d for 10-12 weeks or 50,000 IU on one or two occasions. Biochemical analysis was repeated following supplementation.
  
  
  RESULTS
  Median 25(OH)D of all athletes at baseline was 48.4 nmol/L. Vitamin D insufficiency/deficiency (serum 25(OH)D <50 nmol/L) was particularly evident among GAA players (94%) due to month of sampling. Wintertime supplementation (all doses) significantly increased 25(OH)D (median 62.8 nmol/L at baseline vs. 71.1 nmol/L in April or May; p = .001) and corrected any insufficiencies/deficiencies in this subset of athletes. In contrast, 25(OH)D significantly decreased in those that did not receive a vitamin D supplement, with 74% of athletes classed as vitamin D insufficient/deficient after winter, compared with only 35% at baseline.
  
  
  CONCLUSIONS
  This study has highlighted a high prevalence of vitamin D insufficiency/ deficiency among elite Irish athletes and demonstrated that wintertime vitamin D3 supplementation is an appropriate regimen to ensure vitamin D sufficiency in athletes during winter and early spring.
authors.affiliation: Northern Ireland Centre for Food and Health, University of Ulster, Coleraine, Northern Ireland.
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Magee
authors.forename: L Kirsty
authors.initials: LK
authors.lastname: Pourshahidi
authors.forename: Julie M W
authors.initials: JM
authors.lastname: Wallace
authors.forename: John
authors.initials: J
authors.lastname: Cleary
authors.forename: Joe
authors.initials: J
authors.lastname: Conway
authors.forename: Edward
authors.initials: E
authors.lastname: Harney
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Madigan
mesh_terms: D056352:Athletes; D001914:Boxing; D002118:Calcium / Q000097:blood; D002762:Cholecalciferol / Q000097:blood / Q000494:pharmacology / Q000627:therapeutic use*; D019587:Dietary Supplements; D006233:Persons with Disabilities; D006304:Health Status; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D010281:Parathyroid Hormone / Q000097:blood; D015995:Prevalence; D012621:Seasons; D013177:Sports; D013472:Sunlight; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000188:drug therapy* / Q000453:epidemiology; D014815:Vitamins / Q000097:blood / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D010281:Parathyroid Hormone; D014815:Vitamins; D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D; D002118:Calcium