Effect of Vitamin E on Serum Adiponectin and Leptin in Adults: A Systematic Review and Meta-analysis.

Abstract

Adiponectin and leptin are pivotal adipokines regulating metabolic homeostasis, with dysregulation linked to obesity, insulin resistance, and related metabolic disorders. Vitamin E, a potent antioxidant, has been proposed to modulate adipokine secretion, but existing studies report inconsistent findings. This systematic review and meta-analysis aimed to evaluate the impact of vitamin E oral supplementation on serum adiponectin and leptin levels in adults. Systematic searches were performed in major electronic databases up to August 2025 to identify eligible randomized controlled trials (RCTs). Extracted data were analyzed using STATA, and pooled effect estimates were calculated as weighted mean differences (WMDs) with 95% confidence intervals (CIs). The pooled analysis of 10 RCTs (14 effect sizes) showed that vitamin E supplementation did not significantly alter serum adiponectin (WMD: 0.67 ng/mL; 95% CI: [-0.11 - 1.44]; p = 0.093) or leptin levels (WMD: -3.60 ng/mL; 95% CI: [-7.45 - 0.25]; p = 0.067). Subgroup analyses revealed that long-term supplementation (>12 wk) significantly increased adiponectin (WMD: 1.60 ng/mL; p = 0.039), particularly in patients with nonalcoholic fatty liver disease (NAFLD) (WMD: 4.28 ng/mL; p < 0.001). Additionally, vitamin E significantly reduced leptin levels in NAFLD patients (WMD: -5.45 ng/mL; p < 0.001). This meta-analysis found no significant overall effect of vitamin E on adiponectin and leptin levels; however, long-term supplementation appears beneficial, particularly in patients with NAFLD. Heterogeneity in study design, dosage, and duration highlights the need for further well-designed RCTs to clarify the metabolic and therapeutic roles of vitamin E.