title: Vitamin D in Norwegian renal transplant recipients: A longitudinal study with repeated measurements in winter and summer.
abstract: BACKGROUND
  Organ transplant recipients (OTR) have an increased risk of non-melanoma skin cancer (NMSC) and are advised to avoid direct sunlight. OTR living in the Nordic countries are especially vulnerable to hypovitaminosis D as vitamin D production in the skin is restricted to the summer months.
  
  
  OBJECTIVE
  To investigate constitutional and external factors predicting hypovitaminosis and seasonal variation of vitamin D in renal transplant recipients (RTR) living in the vicinity of Oslo (59(o) N).
  
  
  METHODS
  Ninety-four RTR were included. Interviews covering dietary intake of vitamin D and sun exposure were performed and blood samples were collected in February and August 2013. Results Mean age of patients was 56.8 years and mean graft age 14.5 years. The mean daily total vitamin D intake was 11.8 μg, and the prevalence of hypovitaminosis D (<75 nmol/L) was 67.0% in winter and 56.4% in summer. Sunscreen users had significantly higher 25(OH)D than non-users (p = 0.03). Excluding patients having travelled to southern latitudes during the last three months before blood sampling, no statistical difference was found between winter and summer values of vitamin D (p = 0.60). Being male or having red/light blond hair colour increased vitamin D values significantly from winter to summer.
  
  
  CONCLUSIONS
  Hypovitaminosis D is relatively frequent in Norwegian RTR but not as frequent as earlier reported in studies of RTR from lower latitudes. Lack of seasonal variation in vitamin D may be explained by sun protective behaviour and high dietary intake of vitamin D among patients in this study.
authors.affiliation: Department of Dermatology, Oslo University Hospital, Rikshospitalet, 0027 Oslo, Norway, Department of Dermatology, Oslo University Hospital, Rikshospitalet and Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Syed Mohammad Husain
authors.initials: SM
authors.lastname: Rizvi
authors.affiliation: Department of Biostatistics,, Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
authors.forename: Marit B
authors.initials: MB
authors.lastname: Veierød
authors.affiliation: Hormone Laboratory, Department of Biochemistry, Oslo University Hospital, Aker Hospital, Norway.
authors.forename: Per Medbøe
authors.initials: PM
authors.lastname: Thorsby
authors.affiliation: Department of Dermatology, Oslo University Hospital, Rikshospitalet, 0027 Oslo, Norway.
authors.forename: Per
authors.initials: P
authors.lastname: Helsing
mesh_terms: D004032:Diet; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D016030:Kidney Transplantation; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D012621:Seasons; D013472:Sunlight; D013473:Sunscreening Agents; D014807:Vitamin D / Q000097:blood; D014808:Vitamin D Deficiency / Q000453:epidemiology*
chemical_list: D013473:Sunscreening Agents; D014807:Vitamin D
keywords: Non-melanoma skin cancer; Vitamin D; organ transplant recipients; renal transplant recipients; seasonal variation vitamin D; skin cancer