title: Vitamin D supplementation during Antarctic winter.
abstract: BACKGROUND
  Persons with limited exposure to ultraviolet B light, including space travelers, may not receive enough vitamin D. Recent studies indicate that optimal serum 25-hydroxyvitamin D [25(OH)D] should be > or = 80 nmol/L.
  
  
  OBJECTIVE
  This study was designed to evaluate the effectiveness of 3 doses of vitamin D to raise and maintain 25(OH)D to a concentration >80 nmol/L in persons with limited ultraviolet B light exposure.
  
  
  METHODS
  This was a 5-mo, prospective, randomized, double-blind study of vitamin D supplementation. It was conducted during winter in Antarctica at the McMurdo Station, when ultraviolet B radiation levels are essentially zero. The 55 subjects were randomly divided into 3 groups for vitamin D supplementation: 2000 IU/d (n = 18), 1000 IU/d (n = 19), and 400 IU/d (n = 18). An additional 7 subjects did not take supplements or took supplements of their own choosing. Blood samples were collected about every 2 mo during the winter.
  
  
  RESULTS
  About 5 mo after supplementation started, 25(OH)D increased to 71 +/- 23 nmol/L in the 2000-IU/d group, 63 +/- 25 nmol/L in the 1000-IU/d group, and 57 +/- 15 nmol/L in the 400-IU/d group and decreased to 34 +/- 12 nmol/L in the group not taking supplements.
  
  
  CONCLUSIONS
  These data will enable us to provide space crews with evidence-based recommendations for vitamin D supplementation. The findings also have implications for other persons with limited ultraviolet light exposure, including polar workers and the elderly.
authors.affiliation: Space Life Sciences Directorate, NASA Johnson Space Center, Houston, TX 77058, USA. scott.m.smith@nasa.gov
authors.forename: Scott M
authors.initials: SM
authors.lastname: Smith
authors.forename: Keri K
authors.initials: KK
authors.lastname: Gardner
authors.forename: James
authors.initials: J
authors.lastname: Locke
authors.forename: Sara R
authors.initials: SR
authors.lastname: Zwart
mesh_terms: D000328:Adult; D000864:Antarctic Regions; D050071:Bone Density Conservation Agents / Q000008:administration & dosage* / Q000096:biosynthesis; D004032:Diet; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012621:Seasons; D013472:Sunlight; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000517:prevention & control
chemical_list: D050071:Bone Density Conservation Agents; D014807:Vitamin D; C104450:25-hydroxyvitamin D