Vitamin E and Multiple Health Outcomes: An Umbrella Review of Meta-Analyses

Abstract

The relationship between vitamin E intake or circulating α-tocopherol and various health outcomes is still debatable and uncertain. We conducted an umbrella review to identify the relationships between vitamin E intake or circulating tocopherol and health outcomes by merging and recalculating earlier meta-analyses. The connections that were found to be statistically significant were then classified into different evidence levels based on p values, between-study heterogeneity, prediction intervals, and small study effects. We finally included 32 eligible meta-analyses with four vitamin E sources and 64 unique health outcomes. Only the association between circulating α-tocopherol and wheeze or asthma in children was substantiated by consistent evidence. Suggestive evidence was suggested for seven results on endothelial function (supplemental vitamin E): serum C-reactive protein (CRP) concentrations (supplemental vitamin E), cervical cancer (dietary vitamin E), esophageal cancer (dietary vitamin E), cervical intraepithelial neoplasia (CIN, dietary vitamin E), pancreatic cancer (total vitamin E intake), and colorectal cancer (circulating α-tocopherol levels); all of these showed a protective effect consistent with the vitamin E source. In conclusion, our work has indicated that vitamin E is protective for several particular health outcomes. Further prospective studies are required when other factors that may contribute to bias are considered.