The effect of vitamin E supplementation on serum low-density lipoprotein oxidization: A systematic review and meta-analysis of clinical trials

Abstract

Oxidation of low-density lipoprotein (LDL) accelerates atherosclerosis. Vitamin E is a powerful fat-soluble antioxidant; some studies have shown its beneficial effects in reducing oxidized LDL levels. Due to the inconsistent reports, we performed a systematic review and meta-analysis to evaluate the impact of vitamin E supplementation on oxidation of LDL levels. PubMed, Scopus, Web of Science, and Google Scholar were systematically searched to find clinical trials published in English. A total of 21 records with 29 intervention arms were included in this review. In the meta-analysis of 6 studies that reported changes in oxidized LDL levels, a significant decrease in LDL oxidation was observed (95 CI: -1.44 -2.5, -0.38; I-2 = 95.8%, P < 0.001; Tau-squared: 1.6171). Moreover, a meta-analysis of 7 studies that reported lag time as a measure of LDL oxidation showed that vitamin E supplementation significantly increased the lag time of LDL oxidation (95% CI: 20.45 12.46, 28.43; I-2 = 95.9%, P < 0.001; Tau-squared: 103.3545). Two studies used the thiobarbituric acid-reactive substances (TBARS) assay to evaluate the susceptibility to LDL oxidation. One of them showed a significant decrease in LDL susceptibility to oxidation after supplementation with tocopherol, while the other one did not show a significant effect. Vitamin E significantly reduced the susceptibility of LDL to oxidation and increased the lag time of LDL oxidation.