title: Vitamin D levels after UVB radiation: effects by UVA additions in a randomized controlled trial.
abstract: BACKGROUND
  Ultraviolet B (UVB) radiation increases the serum level of 25-hydroxyvitamin D [25(OH)D]. However, the impact of UVA on vitamin D synthesis by UVB is poorly understood clinically.
  
  
  OBJECTIVE
  To examine how different combinations of UVA and UVB radiation affect S-25(OH)D for the same vitamin D-weighted exposure.
  
  
  METHODS
  Healthy participants were recruited and subsequently divided into four comparable groups regarding initial 25(OH)D value. The different radiations given were whole-body UVB (n = 23), UVAB (n = 23) and UVA (n = 10). The controls (n = 19) had no intervention. The exposure times were chosen to give the same calculated vitamin D effective dose (suberythemal exposures ≤1 standard erythema dose). Blood samples were collected before the first irradiation (t0), immediately after the last (fifth) irradiation (t1) and then after another 2 days after the last (fifth) irradiation (t2).
  
  
  RESULTS
  UVB and UVAB radiation significantly increased 25(OH)D levels. In the UVA group the increase was less with the same vitamin D-weighted radiation dose.
  
  
  CONCLUSIONS
  Short sessions of UVB or UVAB radiation with the same vitamin D-weighted exposure increased 25(OH)D levels. The UVA dose does not influence 25(OH)D levels under short exposure times. However, there was a significantly lower increase of 25(OH)D levels during longer UVA irradiation (≥9 min).
authors.affiliation: Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ellinor
authors.initials: E
authors.lastname: Sallander
authors.forename: Ulf
authors.initials: U
authors.lastname: Wester
authors.forename: Emil
authors.initials: E
authors.lastname: Bengtsson
authors.forename: Desiree
authors.initials: D
authors.lastname: Wiegleb Edström
mesh_terms: D000328:Adult; D000368:Aged; D002117:Calcitriol / Q000097:blood*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014466:Ultraviolet Rays
chemical_list: D002117:Calcitriol
keywords: 25(OH)D; UVA; UVB; sunbeds; vitamin D