title: Recommended summer sunlight exposure amounts fail to produce sufficient vitamin D status in UK adults of South Asian origin.
abstract: BACKGROUND
  The cutaneous synthesis of vitamin D is dependent on UVB from sunlight, but melanin reduces the penetration of UVB and thus contributes to vitamin D insufficiency in individuals with darker skin. The national guidance provided on amounts of sunlight exposure in the United Kingdom is for the light-skinned population, and in the absence of dedicated information, darker-skinned people may attempt to follow this guidance.
  
  
  OBJECTIVE
  We determined the relative effect of a simulation of UK recommendations of summer sunlight exposure on the vitamin D status of individuals of South Asian ethnicity compared with that of whites.
  
  
  METHODS
  In a prospective cohort study, simulated summer sunlight exposures were provided under rigorous dosimetric conditions to 15 adults (aged 20-60 y) of South Asian ethnicity, and serum 25-hydroxyvitamin D [25(OH)D] was measured weekly. Dietary vitamin D intake was estimated. Outcomes were compared with those of 109 whites (aged 20-60 y) treated with the identical UV-radiation exposure protocol.
  
  
  RESULTS
  At baseline (winter trough), all South Asians were vitamin D-insufficient [25(OH)D concentrations <20 ng/mL], and 27% of South Asians were vitamin D-deficient [25(OH)D concentrations <5 ng/mL]; although 25(OH)D concentrations increased postcourse (P < 0.0001), all South Asians remained vitamin D-insufficient. The mean increase in 25(OH)D was 4.3 compared with 10.5 ng/mL in the South Asian and white groups, respectively (P < 0.0001), and 90% of the white group reached vitamin D sufficiency postcourse. The median dietary vitamin D intake was very low in both groups.
  
  
  CONCLUSIONS
  Sunlight-exposure recommendations are inappropriate for individuals of South Asian ethnicity who live at the UK latitude. More guidance is required to meet the vitamin D requirements of this sector of the population. This study was registered at www.isrctn.org as ISRCTN 07565297.
authors.affiliation: Dermatological Sciences, Inflammation Sciences Research Group, School of Translational Medicine, University of Manchester, United Kingdom.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Farrar
authors.forename: Richard
authors.initials: R
authors.lastname: Kift
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Felton
authors.forename: Jacqueline L
authors.initials: JL
authors.lastname: Berry
authors.forename: Marie T
authors.initials: MT
authors.lastname: Durkin
authors.forename: Donald
authors.initials: D
authors.lastname: Allan
authors.forename: Andy
authors.initials: A
authors.lastname: Vail
authors.forename: Ann R
authors.initials: AR
authors.lastname: Webb
authors.forename: Lesley E
authors.initials: LE
authors.lastname: Rhodes
mesh_terms: D000328:Adult; D001208:Asia / Q000208:ethnology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D011446:Prospective Studies; D012621:Seasons; D013472:Sunlight; D006113:United Kingdom; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000096:biosynthesis* / Q000097:blood; D055815:Young Adult
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D