Vitamin D production after UVB exposure – A comparison of exposed skin regions

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 2015-02, Vol.143, p.38-43
• Main Authors: Osmancevic, Amra, Sandström, Katarina, Gillstedt, Martin, Landin-Wilhelmsen, Kerstin, Larkö, Olle, Wennberg Larkö, Ann-Marie, F. Holick, Michael, Krogstad, Anne-Lene
• Format: Article
• Language: English
• Subjects: Adult; Aged; Calcifediol - biosynthesis; Calcifediol - blood; Cholecalciferol - biosynthesis; Cholecalciferol - blood; Dermatologi och venereologi; Dermatology and Venereal Diseases; Female; Humans; Male; Middle Aged; Skin - metabolism; Skin - radiation effects; Ultraviolet Rays
• ISSN: 1011-1344; 1873-2682; 1873-2682
• DOI: 10.1016/j.jphotobiol.2014.12.026

•Serum cholecalciferol and 25(OH)D3 increased after UVB irradiation of 3 different anatomic sites in the same individuals.•UVB exposure of a larger skin area resulted in greater increases in serum cholecalciferol concentrations.•Sporadic exposure of only face and hands was capable of a significant rise in serum concentrations of 25(OH)D3. Cholecalciferol is an essential steroid produced in the skin by solar ultraviolet B radiation (UVB 290–315nm). Skin production of cholecalciferol depends on factors affecting UVB flux, age and exposed skin area. Serum cholecalciferol and 25-hydroxyvitamin D3 [25(OH)D3] concentrations were measured after UVB irradiation of 3 different skin areas to compare the skin capacity to produce vitamin D in different anatomic sites in the same individuals. Ten voluntary Caucasians (skin photo type II & III, aged 48±12years (±SD)) were exposed to broadband UVB (280–320nm) between February and April. Hands and face, upper body and whole body were exposed to a suberythemic dose of UVB (median 101mJ/cm2 (min 66, max 143)) (for 3 subsequent days 24h apart with a wash out period of about 3weeks (median 18days (min 11, max 25)) between the exposures of respective area. Serum concentrations of cholecalciferol and 25(OH)D3, were measured immediately before the first and 24h after the last dose of radiation. There was a significantly higher increase in serum cholecalciferol after UVB exposure of the two larger skin areas compared to face and hands, but no difference in increase was found between upper body and whole body exposures. Exposure of a larger skin area was superior to small areas and gave greater increase in both serum cholecalciferol and serum 25(OH)D3 concentrations. However, exposure of face and hands, i.e. only 5% of the body surface area, was capable of increasing serum concentrations of 25(OH)D3.