Document Type: Review Article
Department of Clinical Nutrition, School of Nutrition and Food Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
Nutrition Research Center, Department of Clinical Nutrition, School of Nutrition and Food Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
Current results from clinical trials about vitamin E effects on adiponectin are ambiguous. Therefore, we conducted a meta-analysis of available RCTs to resolve this inconsistency. The systematic search was performed in several databases including SCOPUS, PubMed-Medline, and Google Scholar until October 1st, 2017. We used fixedeffects model in combination with mean difference (MD) and 95% confidence intervals (CI) for the analysis of data. Meta-analysis of 6 RCTs (9 treatment arms) showed a significant increase in circulating adiponectin levels (MD: 0.36 ug/ml, 95% CI: 0.16 to 0.56; p<0.001), following vitamin E supplementation. In sub-group analysis, a significant increasing effect was observed only in trials with ≥400 mg/day dosage (MD: 0.78 ug/ml, 95% CI: 0.31, 1.24, p=0.001) and those trials lasting ≥6 months (MD: 0.58 ug/mL, 95% CI: 0.29, 0.86, p<0.001). In meta-regression, there was association between changes in adiponectin concentrations and duration of supplementation. Our findings showed the significant increase effect of vitamin E supplementation on circulating adiponectin levels, however a significant increasing effect was observed at doses above 400 mg/day and when supplementation lasting over 6 months.