title: Blood vitamin D status and metabolic syndrome in the general adult population: a dose-response meta-analysis.
abstract: BACKGROUND
  Increasing evidence has suggested an association between blood vitamin D levels and metabolic syndrome.
  
  
  OBJECTIVE
  Our objective was to determine the relationship between blood vitamin D status and metabolic syndrome in the general adult population, using a dose-response meta-analysis.
  
  
  METHODS
  We searched the PubMed, EMBASE, Web of Science, and Cochrane Library databases through July 2013 to identify relevant studies.
  
  
  METHODS
  Observational studies, reporting risk ratios with a 95% confidence interval (CI) for metabolic syndrome in ≥3 categories of blood 25-hydroxyvitamin D [25(OH)D] levels, were selected.
  
  
  METHODS
  Data extraction was performed independently by 2 authors, and the quality of the studies was evaluated using the risk of bias assessment tool for nonrandomized studies.
  
  
  RESULTS
  The pooled odds ratio of metabolic syndrome per 25 nmol/L increment in the serum/plasma 25(OH)D concentration was 0.87 (95% CI = 0.83-0.92, I(2) = 85%), based on 16 "cross-sectional studies" and 1.00 (95% CI = 0.98-1.02, I(2) = 0%) for 2 "cohort and nested case-control studies." The dose-response meta-analysis showed a generally linear, inverse relationship between 25(OH)D levels and metabolic syndrome in the cross-sectional studies (P for linear trend < .001).
  
  
  CONCLUSIONS
  Blood vitamin D levels were associated with a risk of metabolic syndrome in cross-sectional studies but not in longitudinal studies. Randomized, clinical trials will be necessary to address the issue of causality and to determine whether vitamin D supplementation is effective for the prevention of metabolic syndrome.
authors.affiliation: Department of Family Medicine (S.Y.J.), Yeouido St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul 150-713, Korea; Department of Preventive Medicine (H.S.J.), Seoul St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea; and Department of Family Medicine (D.H.K.), Korea University Ansan Hospital, Korea University College of Medicine, Seoul 136-705, Korea.
authors.forename: Sang Yhun
authors.initials: SY
authors.lastname: Ju
authors.forename: Hyun Suk
authors.initials: HS
authors.lastname: Jeong
authors.forename: Do Hoon
authors.initials: DH
authors.lastname: Kim
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003430:Cross-Sectional Studies / Q000706:statistics & numerical data; D006801:Humans; D024821:Metabolic Syndrome / Q000097:blood* / Q000453:epidemiology*; D064887:Observational Studies as Topic / Q000706:statistics & numerical data; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D