Martens LG, Luo J, van Dijk KW, et al. - In this study, no evidence was found for a causal link between dietary‐derived antioxidant levels and ischemic stroke. Hence, antioxidant supplementation is unlikely to be clinically beneficial to avert ischemic stroke.

• The links between genetically influenced antioxidant levels in blood and ischemic stroke were assessed using Mendelian randomization in this study.

• Independent genetic instrumental variables were selected for each circulating antioxidant (vitamins E and C, lycopene, β‐carotene, and retinol), and summary statistics for single‐nucleotide polymorphisms–stroke links were used from 3 European‐ancestry cohorts (cases/controls).

• None of the genetically influenced absolute antioxidants or antioxidant metabolite levels were causally related to a lower risk of ischemic stroke, in an integrated sample of 1,058,298 persons (70,791 cases).

• The estimated odds ratios (ORs) for absolute antioxidants levels ranged between 0.94 for vitamin C and 1.04 for lycopene.

• ORs, for metabolites, ranged between 1.01 for retinol and 1.12 for vitamin E.