title: Effect of vitamin D supplementation and ultraviolet B exposure on serum 25-hydroxyvitamin D concentrations in healthy volunteers: a randomized, crossover clinical trial.
abstract: BACKGROUND
  Solar ultraviolet (UV) radiation during the summer and vitamin D supplementation are two major sources of vitamin D for humans at northern latitudes. However, little is known about the relative efficiency of these two vitamin D sources.
  
  
  OBJECTIVE
  The main goal was to compare the efficiency of high-dose oral vitamin D3 supplementation (2000 IU per day for 30 days) with a simulated summer UV exposure [10 sunbed sessions to a total dose of 23·8 standard erythema doses (SED)] to improve vitamin D status.
  
  
  METHODS
  Healthy volunteers were randomized into two groups: group 1 received vitamin D supplementation followed by 10 whole-body sunbed exposures; group 2 started with 10 sunbed exposures followed by vitamin D supplementation.
  
  
  RESULTS
  The oral supplementation with vitamin D3 resulted in a mean (SEM) serum 25-hydroxyvitamin D [25(OH)D] increase of 25·3 (5·4) nmol L(-1) . A similar increase, 19·8 (5·4) nmol L(-1) , was observed after simulated summer UV exposure. At the end of the study, serum 25(OH)D concentrations were similar in both groups.
  
  
  CONCLUSIONS
  Twice-weekly whole-body sunbed exposure to a dose of 4·8 SED is equal to 2000 IU daily of oral vitamin D supplementation for 30 days and enough to achieve and maintain serum 25(OH)D concentrations > 75 nmol L(-1) in ~55% of cases. Based on our calculations, this dose corresponds to a cumulative weekly whole-body exposure of 3·4 SED (~ 40 min around midday during the summer at the latitude of Oslo).
authors.affiliation: Department of Radiation Biology, Oslo University Hospital the Norwegian Radium Hospital, Montebello, Oslo, Norway.
authors.forename: Z
authors.initials: Z
authors.lastname: Lagunova
authors.forename: A C
authors.initials: AC
authors.lastname: Porojnicu
authors.forename: L
authors.initials: L
authors.lastname: Aksnes
authors.forename: M F
authors.initials: MF
authors.lastname: Holick
authors.forename: V
authors.initials: V
authors.lastname: Iani
authors.forename: O S
authors.initials: OS
authors.lastname: Bruland
authors.forename: J
authors.initials: J
authors.lastname: Moan
mesh_terms: D000284:Administration, Oral; D000328:Adult; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D012621:Seasons; D013472:Sunlight; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000378:metabolism; D014815:Vitamins / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D014815:Vitamins; D014807:Vitamin D; C104450:25-hydroxyvitamin D