Many lines of evidence suggest that oxidative stress is important in the pathogenesis of Alzheimer disease. In particular, ß-amyloid, which is found abundantly in the brains of Alzheimer disease patients, is toxic in neuronal cell cultures through a mechanism involving free radicals. Vitamin E prevents the oxidative damage induced by ß-amyloid in cell culture and delays memory deficits in animal models.
A placebo-controlled, clinical trial of vitamin E in patients with moderately advanced Alzheimer disease was conducted by the Alzheimer's Disease Cooperative Study. Subjects in the vitamin E group were treated with 2000 IU (1342 
-tocopherol equivalents) vitamin E/d.
The results indicated that vitamin E may slow functional deterioration leading to nursing home placement. A new clinical trial is planned that will examine whether vitamin E can delay or prevent a clinical diagnosis of Alzheimer disease in elderly persons with mild cognitive impairment.