Long-term vitamin E doesn't enhance congnitive function

A subset of women from the Women's Health Study, a randomized, double-blind, placebo-controlled trial, participated in a study to determine if 600 IU of α-tocopherol taken on alternate days has any effects on general cognition, verbal memory, or category fluency in generally healthy older women.

Unfortunately, data from 10 years of treatment and 4 years of follow-up revealed no indication that vitamin E provides any overall cognitive benefits. At each cognitive assessment (the first at 5.6 years after randomization and the last at 9.6 years), the researchers observed no differences in global scores between the vitamin E and placebo groups. And the risk for substantial decline in the global score in the vitamin E group versus the placebo group was 0.92 (95% CI, 0.77–1.10).

The authors say the lack of findings could be due to the dose of vitamin E being too low, that the supplements used in the study contained mostly α-tocopherols, rather than γ-tocopherols, which may be more beneficial, or that the duration of use, although long in the study, was insufficient. Perhaps the supplements must be started prior to the sixth decade of life. Vitamin E supplementation for 10 years or less does not seem to provide any sort of neuroprotection.