title: Size of the exposed body surface area, skin erythema and body mass index predict skin production of vitamin D.
abstract: BACKGROUND
  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.
  
  
  OBJECTIVE
  To examine changes in serum concentrations of cholecalciferol and its metabolites after UVB exposure of different skin areas.
  
  
  METHODS
  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.
  
  
  RESULTS
  Subjects with whole body exposure had an average S-cholecalciferol increase per dose unit of 0.18ngml(-1)mJ(-1)cm(2), 0.95 CI: (0.16, 0.20), upper body treatment 0.13ngml(-1)mJ(-1)cm(2), 0.95 CI: (0.10, 0.15) and face and hands exposure 0.013ngml(-1)mJ(-1)cm(2), 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Dept of Dermatology, Sahlgrenska University Hospital at Sahlgrenska Academy, University of Gothenburg, Sweden. Electronic address: Amra.Osmancevic@vgregion.se.
authors.forename: Amra
authors.initials: A
authors.lastname: Osmancevic
authors.affiliation: Dept of Dermatology, Sahlgrenska University Hospital at Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Gillstedt
authors.affiliation: Institution of Medicine, Sahlgrenska University Hospital at Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Landin-Wilhelmsen
authors.affiliation: Dept of Dermatology, Sahlgrenska University Hospital at Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Ann-Marie
authors.initials: AM
authors.lastname: Wennberg Larkö
authors.affiliation: Dept of Dermatology, Sahlgrenska University Hospital at Sahlgrenska Academy, University of Gothenburg, Sweden.
authors.forename: Olle
authors.initials: O
authors.lastname: Larkö
authors.affiliation: Boston University School of Medicine, Boston, MA 02118, United States.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Holick
authors.affiliation: Dept of Dermatology, Sahlgrenska University Hospital at Sahlgrenska Academy, University of Gothenburg, Sweden; Dept of Dermatology, RH University Hospital, Norway.
authors.forename: Anne-Lene
authors.initials: AL
authors.lastname: Krogstad
mesh_terms: D000328:Adult; D015992:Body Mass Index; D001830:Body Surface Area; D002762:Cholecalciferol / Q000096:biosynthesis* / Q000097:blood; D004307:Dose-Response Relationship, Radiation; D004890:Erythema / Q000097:blood / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011897:Random Allocation; D012621:Seasons; D012867:Skin / Q000378:metabolism* / Q000528:radiation effects; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000097:blood; D055815:Young Adult
chemical_list: D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D
keywords: Cholecalciferol; Skin erythema; Skin surface; UVB-dose; Vitamin D synthesis; Vitamin D(3)