title: Vitamin D and diabetic nephropathy: A systematic review and meta-analysis.
abstract: OBJECTIVE
  There has been a long history documenting the use of different vitamin D derivatives as therapy for renal diseases. However, to our knowledge, there is no comprehensive assessment of the relation between vitamin D deficiency and risk for diabetic nephropathy (DN). Additionally, the effect of vitamin D supplementation on DN is still unclear. The aim of this meta-analysis was to assess these issues by pooling together the results from cross-sectional studies and clinical trials.
  
  
  METHODS
  A systematic literature search of PubMed, Scopus, and Google Scholar was conducted, ending in September 2014. For cross-sectional studies, odds ratio was used as a measure of the association between vitamin D status and risk for DN; for clinical trials, mean and SD of the main outcome (urine albumin-to-creatinine ratio [UACR]) in intervention and placebo groups were considered for analysis.
  
  
  RESULTS
  The final selected articles were published between 2009 and 2014. In all, 3700 and 219 patients were enrolled in observational and interventional studies, respectively. The pooled odds ratio from six cross-sectional studies was 1.80 (95% confidence interval [CI], 1.25-2.59; P = 0.002), indicating a significant inverse association between serum vitamin D status and risk for nephropathy in patients with diabetes. However, the pooled data of UACR levels in clinical trials suggested no significant change following vitamin D supplementation (17.98; 95% CI, -35.35 to 71.32; P = 0.51).
  
  
  CONCLUSIONS
  This meta-analysis showed the higher risk for nephropathy in vitamin D-deficient patients with diabetes. Pooling the results of available clinical trials after vitamin D supplementation did not support causality in this association.
authors.affiliation: Department of Cellular and Molecular Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hoda
authors.initials: H
authors.lastname: Derakhshanian
authors.affiliation: Department of Community Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Sakineh
authors.initials: S
authors.lastname: Shab-Bidar
authors.affiliation: Division of Energy Balance and Obesity, Aberdeen Centre for Energy Regulation and Obesity, Rowett Research Institute, Bucksburn, Aberdeen, Scotland, United Kingdom.
authors.forename: John R
authors.initials: JR
authors.lastname: Speakman
authors.affiliation: Department of Cellular and Molecular Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Hoda
authors.initials: H
authors.lastname: Nadimi
authors.affiliation: Department of Clinical Nutrition, School of Nutritional Sciences and Dietetics, Tehran University of Medical Sciences, Tehran, Iran. Electronic address: kdjafarian@tums.ac.ir.
authors.forename: Kurosh
authors.initials: K
authors.lastname: Djafarian
mesh_terms: D002986:Clinical Trials as Topic; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000097:blood*; D003928:Diabetic Nephropathies / Q000209:etiology*; D019587:Dietary Supplements; D006801:Humans; D008875:Middle Aged; D014807:Vitamin D / Q000008:administration & dosage / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications* / Q000188:drug therapy*; D014815:Vitamins / Q000008:administration & dosage / Q000097:blood
chemical_list: D014815:Vitamins; D014807:Vitamin D
keywords: Cholecalciferol; Diabetes mellitus; Nephropathy