title: Meta-analysis: vitamin D and non-alcoholic fatty liver disease.
abstract: BACKGROUND
  Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent condition. Emerging evidence suggests that vitamin D may play a role in the pathogenesis of NAFLD.
  
  
  OBJECTIVE
  To review systematically the association between vitamin D levels, measured as serum 25-hydroxy vitamin D [25(OH)D], and NAFLD.
  
  
  METHODS
  We used PubMed and EMBASE databases to identify all studies that assessed the association between vitamin D and NAFLD up until 22 April 2013, without language restrictions. We included studies that compared vitamin D levels between NAFLD cases and controls and also those that compared the odds of vitamin D deficiency by NAFLD status. Pooled standardised differences and odds ratios were calculated using an inverse variance method.
  
  
  RESULTS
  Seventeen cross-sectional and case-control studies have evaluated the association between vitamin D and NAFLD. NAFLD was diagnosed using biopsy (4 studies), ultrasound or CT (10 studies) and liver enzymes (3 studies). Nine studies provided data for a quantitative meta-analysis. Compared to controls, NAFLD patients had 0.36 ng/mL (95% CI: 0.32, 0.40 ng/mL) lower levels of 25(OH)D and were 1.26 times more likely to be vitamin D deficient (OR 1.26, 95% CI: 1.17, 1.35).
  
  
  CONCLUSIONS
  NAFLD patients have decreased serum 25(OH)D concentrations, suggesting that vitamin D may play a role in the development of NAFLD. The directionality of this association cannot be determined from cross-sectional studies. Demonstration of a causal role of hypovitaminosis D in NAFLD development in future studies could have important therapeutic implications.
authors.affiliation: Department of Medicine, Medstar Washington Hospital Center, Washington, DC 20010, USA. eliadesm@yahoo.com
authors.forename: M
authors.initials: M
authors.lastname: Eliades
authors.forename: E
authors.initials: E
authors.lastname: Spyrou
authors.forename: N
authors.initials: N
authors.lastname: Agrawal
authors.forename: M
authors.initials: M
authors.lastname: Lazo
authors.forename: F L
authors.initials: FL
authors.lastname: Brancati
authors.forename: J J
authors.initials: JJ
authors.lastname: Potter
authors.forename: A A
authors.initials: AA
authors.lastname: Koteish
authors.forename: J M
authors.initials: JM
authors.lastname: Clark
authors.forename: E
authors.initials: E
authors.lastname: Guallar
authors.forename: R
authors.initials: R
authors.lastname: Hernaez
mesh_terms: D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005234:Fatty Liver / Q000097:blood / Q000209:etiology*; D006801:Humans; D065626:Non-alcoholic Fatty Liver Disease; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications*
chemical_list: D014807:Vitamin D