title: Vitamin D and histologic severity of nonalcoholic fatty liver disease: A systematic review and meta-analysis.
abstract: BACKGROUND
  NAFLD and vitamin D deficiency often coexist and epidemiologic evidence has shown that both of these conditions share several risk factors. Recent studies investigating the relationship between vitamin D levels and severity of NAFLD showed conflicting results. Thus we conducted a systematic review and meta-analysis to evaluate association between vitamin D and NAFLD histologic severity.
  
  
  METHODS
  A comprehensive search of the databases of the MEDLINE and EMBASE was performed from inception through November 2016. Observational studies compared serum vitamin D levels among NAFLD patients with high and low histologic severity, which was determined by NAFLD activity score (NAS) and fibrosis score. We calculated pooled mean difference (MD) of 25-hydroxyvitamin D levels with 95% confidence intervals (CI) using random-effects model.
  
  
  RESULTS
  Data were extracted from 6 studies involving 974 NAFLD patients. There was no difference in 25-hydroxyvitamin D levels among NAFLD patients with high NAS (score of ≥5) versus low NAS (pooled MD=-0.93, 95%CI -2.45 to 0.58, I2=0%) and also high fibrosis score (score of ≥3) versus low fibrosis score (pooled MD=0.88, 95%CI -2.65 to 4.42, I2=64%).
  
  
  CONCLUSIONS
  Despite evidence implicating vitamin D in NAFLD pathogenesis, serum 25-hydroxyvitamin D may not be associated with NAFLD histologic severity.
authors.affiliation: Department of Internal Medicine, University of Hawaii, Honolulu, HI, USA; Department of Internal Medicine, King Chulalongkorn Memorial Hospital, Bangkok, Thailand. Electronic address: veeravich_j@hotmail.com.
authors.forename: Veeravich
authors.initials: V
authors.lastname: Jaruvongvanich
authors.affiliation: Department of Internal Medicine, Norwalk Hospital, Norwalk, CT, USA. Electronic address: dr.ahuja.wasin@gmail.com.
authors.forename: Wasin
authors.initials: W
authors.lastname: Ahuja
authors.affiliation: Department of Internal Medicine, Bassett Medical Center and Columbia University College of Physicians and Surgeons, Cooperstown, NY, USA; Department of Preventive and Social Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand. Electronic address: anawin.sanguankeo@bassett.org.
authors.forename: Anawin
authors.initials: A
authors.lastname: Sanguankeo
authors.affiliation: Department of Internal Medicine, Bassett Medical Center and Columbia University College of Physicians and Surgeons, Cooperstown, NY, USA. Electronic address: dr.karn.wi@gmail.com.
authors.forename: Karn
authors.initials: K
authors.lastname: Wijarnpreecha
authors.affiliation: Department of Internal Medicine, Bassett Medical Center and Columbia University College of Physicians and Surgeons, Cooperstown, NY, USA; Department of Preventive and Social Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Thailand. Electronic address: sikarin.upala@bassett.org.
authors.forename: Sikarin
authors.initials: S
authors.lastname: Upala
mesh_terms: D015415:Biomarkers / Q000097:blood; D006801:Humans; D008099:Liver / Q000473:pathology*; D065626:Non-alcoholic Fatty Liver Disease / Q000097:blood* / Q000473:pathology*; D012307:Risk Factors; D012720:Severity of Illness Index; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications*
chemical_list: D015415:Biomarkers; D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: Fibrosis; Liver histology; Meta-analysis; NAFLD activity score; Nonalcoholic fatty liver disease; Vitamin D