title: The determinants of serum vitamin D levels in participants in a melanoma case-control study living in a temperate climate.
abstract: BACKGROUND
  We report the determinants of serum levels of vitamin D in a U.K. melanoma case-control study benefitting from detailed exposure and genotyping data.
  
  
  METHODS
  Sun exposure, supplemental vitamin D, and SNPs reported to be associated with serum levels were assessed as predictors of a single serum 25-hydroxyvitamin D3 measurement adjusted for season, age, sex, and body mass index.
  
  
  RESULTS
  Adjusted analyses showed that vitamin D levels were sub-optimal especially in the sun-sensitive individuals (-2.61 nmol/L, p = 0.03) and for inheritance of a genetic variant in the GC gene coding for the vitamin D-binding protein (-5.79 for heterozygotes versus wild type, p = <0.0001). Higher levels were associated with sun exposure at the weekend in summer (+4.71 nmol/L per tertile, p = <0.0001), and on hot holidays (+4.17 nmol/L per tertile, p = <0.0001). In smoothed scatter plots, vitamin D levels of 60 nmol/L in the non-sun-sensitive individuals were achieved after an average 6 h/day summer weekend sun exposure but not in the sun-sensitive individuals. Users of supplements had levels on average 11.0 nmol/L higher, p = <0.0001, and achieved optimal levels irrespective of sun exposure.
  
  
  CONCLUSIONS
  Sun exposure was associated with increased vitamin D levels, but levels more than 60 nmol/L were reached on average only in individuals reporting lengthy exposure (≥12 h/weekend). The sun-sensitive individuals did not achieve optimal levels without supplementation, which therefore should be considered for the majority of populations living in a temperate climate and melanoma patients in particular. Inherited variation in genes such as GC is a strong factor, and carriers of variant alleles may therefore require higher levels of supplementation.
authors.affiliation: Section of Epidemiology and Biostatistics, Leeds Institute of Molecular Medicine, University of Leeds, Cancer Genetics Building, St James's Hospital, Beckett Street, Leeds, LS9 7TF, UK. J.R.Davies@leeds.ac.uk
authors.forename: John R
authors.initials: JR
authors.lastname: Davies
authors.forename: Yu-Mei
authors.initials: YM
authors.lastname: Chang
authors.forename: Helen
authors.initials: H
authors.lastname: Snowden
authors.forename: May
authors.initials: M
authors.lastname: Chan
authors.forename: Susan
authors.initials: S
authors.lastname: Leake
authors.forename: Birute
authors.initials: B
authors.lastname: Karpavicius
authors.forename: Sue
authors.initials: S
authors.lastname: Haynes
authors.forename: Kairen
authors.initials: K
authors.lastname: Kukalizch
authors.forename: Juliette
authors.initials: J
authors.lastname: Randerson-Moor
authors.forename: Faye
authors.initials: F
authors.lastname: Elliott
authors.forename: Julian
authors.initials: J
authors.lastname: Barth
authors.forename: Peter A
authors.initials: PA
authors.lastname: Kanetsky
authors.forename: Mark
authors.initials: M
authors.lastname: Harland
authors.forename: D Timothy
authors.initials: DT
authors.lastname: Bishop
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Barrett
authors.forename: Julia A
authors.initials: JA
authors.lastname: Newton-Bishop
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D002112:Calcifediol / Q000008:administration & dosage / Q000097:blood*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D002980:Climate; D019587:Dietary Supplements; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006579:Heterozygote; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008545:Melanoma / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D008875:Middle Aged; D012621:Seasons; D012878:Skin Neoplasms / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D013472:Sunlight; D006113:United Kingdom; D014808:Vitamin D Deficiency / Q000097:blood / Q000235:genetics; D014809:Vitamin D-Binding Protein / Q000097:blood / Q000235:genetics; D055815:Young Adult
chemical_list: D014809:Vitamin D-Binding Protein; D002112:Calcifediol