Size of the exposed body surface area, skin erythema and body mass index predict skin production of vitamin D

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 2015-08, Vol.149, p.224-229
• Main Authors: Osmancevic, Amra, Gillstedt, Martin, Landin-Wilhelmsen, Kerstin, Wennberg Larkö, Ann-Marie, Larkö, Olle, Holick, Michael F., Krogstad, Anne-Lene
• Format: Article
• Language: English
• Subjects: Adult; Body Mass Index; Body Surface Area; Cholecalciferol; Cholecalciferol - biosynthesis; Cholecalciferol - blood; Dermatologi och venereologi; Dermatology and Venereal Diseases; Dose-Response Relationship, Radiation; Erythema - blood; Erythema - metabolism; EXPOSURES; Female; Humans; Male; Middle Aged; OBESITY; Random Allocation; Seasons; Skin - metabolism; Skin - radiation effects; Skin erythema; Skin surface; SUNLIGHT; THRESHOLD; Ultraviolet Rays; UVB-dose; Vitamin D - analogs & derivatives; Vitamin D - biosynthesis; Vitamin D - blood; Vitamin D synthesis; Vitamin D-3; Vitamin D3; Young Adult
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2015.06.008

•Serum cholecalciferol was analyzed after UVB exposures of different skin areas.•Exposure of small body surface areas induces less cholecalciferol production.•The increase in cholecalciferol correlated positively to UVB dose and skin erythema.•The increase in cholecalciferol correlated negatively to body mass index (BMI). Cholecalciferol (vitamin D3), produced in the skin by UVB irradiation (290–315nm) of 7-dehydrocholesterol, is metabolized in the liver into 25-hydroxyvitamin D [25(OH)D] which is a major circulating metabolite. To examine changes in serum concentrations of cholecalciferol and its metabolites after UVB exposure of different skin areas. 21 healthy Caucasians (skin type II and III, aged 23–47years) were exposed to broadband UVB (290–320nm) and randomized to either exposure to one minimal erythema dose given as a single dose, or a suberythemic dose given for 3 subsequent days. The following areas were exposed: face and back of hands, upper half of the body and the whole body, respectively. Serum cholecalciferol and 25(OH)D were measured immediately before start and 24h after the 1st and last exposure, respectively. Subjects with whole body exposure had an average S-cholecalciferol increase per dose unit of 0.18ngml−1mJ−1cm2, 0.95 CI: (0.16, 0.20), upper body treatment 0.13ngml−1mJ−1cm2, 0.95 CI: (0.10, 0.15) and face and hands exposure 0.013ngml−1mJ−1cm2, 0.95 CI: (−0.012, 0.037). The increase in cholecalciferol correlated positively to the UVB dose and skin erythema and negatively to body mass index (BMI) when controlling for other factors. Exposure of face and hands induces smaller cholecalciferol production in comparison with exposure of larger skin areas. Size of the exposed skin area, UVB dose, skin erythema and BMI were the major determinants for serum levels of skin synthesized cholecalciferol. Exposure of hands and face induces smaller cholecalciferol production in comparison with exposure of larger skin areas.