Vitamin D levels after UVB radiation: effects by UVA additions in a randomized controlled trial

• Published in: Photodermatology, photoimmunology & photomedicine photoimmunology & photomedicine, 2013-12, Vol.29 (6), p.323-329
• Main Authors: Sallander, Ellinor, Wester, Ulf, Bengtsson, Emil, Wiegleb Edström, Desiree
• Format: Article
• Language: English
• Subjects: 25(OH)D; 25-Hydroxyvitamin D; Adult; Aged; Calcitriol - blood; Dose-Response Relationship, Radiation; Female; Humans; Male; Middle Aged; sunbeds; Ultraviolet Rays; UVA; UVB; vitamin D
• ISSN: 0905-4383; 1600-0781; 1600-0781
• DOI: 10.1111/phpp.12076

Summary 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. Materials and 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).