title: Effect of vitamins C and E on insulin resistance in diabetes: a meta-analysis study.
abstract: BACKGROUND
  Data regarding the effect of vitamin C (VC) and vitamin E (VE) supplementation on insulin resistance in type 2 diabetes mellitus (T2DM) are controversial. We aimed to systematically review the current data on this topic.
  
  
  METHODS
  All randomized controlled trials (RCTs) conducted to assess the effect of VC and/or VE on insulin resistance in diabetes published in Google Scholar and PubMed web databases until January 2014 were included. Exclusion criteria were studies conducted in animal, type 1 DM, children or pregnant women. Main outcome measure was insulin resistance by homoeostasis model assessment (HOMA) index. According to degree of heterogeneity, fixed- or random-effect model was employed by stata software (11.0).
  
  
  RESULTS
  We selected 14 RCTs involving 735 patients with T2DM. VE or mixture-mode supplementation did not have any significant effect on HOMA with a standardized mean difference (SMD): 0·017, 95% CI: -0·376 to 0·411 (P = 0·932); and SMD: -0·035, 95% CI: -0·634 to 0·025 (P = 0·070), respectively, by random-effect model. VC supplement alone did not improve insulin resistance with a SMD: -0·150, 95% CI: -0·494 to 0·194 (P = 0·391), by fixed-effect model. Meta-regression test demonstrated that HOMA index may have not been influenced by the year of publication, dosage or duration of treatment.
  
  
  CONCLUSIONS
  The sole intake of VC, VE or their combination with other antioxidants could not improve insulin resistance in diabetes.
authors: Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors: Mehrnoosh
authors: M
authors: Khodaeian
authors: Diabetes Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors: Ozra
authors: O
authors: Tabatabaei-Malazy
authors: Department of Community Medicine, School of Medicine, Alborz University of Medical Sciences, Karaj, Iran.|Non-Communicable Disease Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran university of Medical Sciences, Tehran, Iran.
authors: Mostafa
authors: M
authors: Qorbani
authors: Non-Communicable Disease Research Center, Endocrinology and Metabolism Population Sciences Institute, Tehran university of Medical Sciences, Tehran, Iran.
authors: Farshad
authors: F
authors: Farzadfar
authors: Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA.
authors: Peyvand
authors: P
authors: Amini
authors: Endocrinology and Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors: Bagher
authors: B
authors: Larijani
mesh_terms: D000975:Antioxidants / Q000627:therapeutic use*; D001205:Ascorbic Acid / Q000627:therapeutic use*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D019587:Dietary Supplements; D006801:Humans; D007333:Insulin Resistance; D016032:Randomized Controlled Trials as Topic; D016896:Treatment Outcome; D014810:Vitamin E / Q000627:therapeutic use*
chemical_list: D000975:Antioxidants; D014810:Vitamin E; D001205:Ascorbic Acid
keywords: Diabetes mellitus; insulin resistance; meta-analysis; systematic review; vitamin C; vitamin E