Effect of vitamins C and E on insulin resistance in diabetes: a meta‐analysis study

Background Data regarding the effect of vitamin C ( VC ) and vitamin E ( VE ) supplementation on insulin resistance in type 2 diabetes mellitus ( T 2 DM ) are controversial. We aimed to systematically review the current data on this topic. Materials and methods All randomized controlled trials ( RCT s) 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 RCT s involving 735 patients with T2 DM . 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.