title: Global vitamin D levels in relation to age, gender, skin pigmentation and latitude: an ecologic meta-regression analysis.
abstract: We performed a meta-analysis of cross-sectional studies on serum 25(OH)D status globally. Serum 25(OH)D levels on average were 54 nmol/l, were higher in women than men, and higher in Caucasians than in non-Caucasians. There was no trend in serum 25(OH)D level with latitude. Vitamin D deficiency was widespread.
  
  
  BACKGROUND
  We studied vitamin D status (expressed as serum 25-hydroxy-vitamin D [25(OH)D]) in native subjects worldwide.
  
  
  METHODS
  Meta-analysis and meta-regression of studies reporting on 25(OH)D in healthy subjects retrieved from Pubmed, Embase and Web of Science using the terms "serum", "25-hydroxy-vitamin D", "cholecalciferol", and "human". A total of 394 studies were included.
  
  
  RESULTS
  The mean 25(OH)D level was 54 nmol/l (95% CI: 52-57 nmol/l). Women had borderline significantly higher 25(OH)D levels than men, and Caucasians had higher levels than non-Caucasians. 25(OH)D levels were higher in subjects aged >15 years than in younger subjects. Unadjusted there was no significant decrease in 25(OH)D with latitude (slope of curve -0.03 +/- 0.12 nmol/l per degree latitude north or south of equator, p = 0.8). There was a significant decline with latitude for Caucasians (-0.69 +/- 0.30 nmol/l per degree, p = 0.02), but not for non-Caucasians (0.03 +/- 0.39 nmol/l per degree, p = 0.14). After adjustment for age, gender, and ethnicity, no overall correlation was present between 25(OH)D and latitude (-0.29 +/- 0.24 nmol/l per degree, p = 0.23).
  
  
  CONCLUSIONS
  There was no overall influence of latitude on 25(OH)D. However, in separate analyses 25(OH)D decreased with latitude in Caucasians but not in non-Caucasians. A widespread global vitamin D insufficiency was present compared with proposed threshold levels.
authors.affiliation: Department of Endocrinology and Metabolism C, Aarhus Amtssygehus, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: T
authors.initials: T
authors.lastname: Hagenau
authors.forename: R
authors.initials: R
authors.lastname: Vest
authors.forename: T N
authors.initials: TN
authors.lastname: Gissel
authors.forename: C S
authors.initials: CS
authors.lastname: Poulsen
authors.forename: M
authors.initials: M
authors.lastname: Erlandsen
authors.forename: L
authors.initials: L
authors.lastname: Mosekilde
authors.forename: P
authors.initials: P
authors.lastname: Vestergaard
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002648:Child; D003430:Cross-Sectional Studies; D004463:Ecology / Q000379:methods; D005006:Ethnicity; D005260:Female; D014943:Global Health; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012737:Sex Factors; D012880:Skin Pigmentation / Q000502:physiology*; D013472:Sunlight; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000453:epidemiology / Q000208:ethnology; D044465:White People
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D