Vitamin E, particularly in the form of alpha-tocopherol, has been investigated as a potential intervention for dementia due to its antioxidant properties, which may help protect neuronal membranes from oxidative damage implicated in neurodegenerative diseases such as Alzheimer's. Several randomized controlled trials and meta-analyses have evaluated Vitamin E supplementation for this purpose. The most notable trial, published in the New England Journal of Medicine (2005), tested high-dose Vitamin E (2000 IU/day) in patients with moderate Alzheimer's disease and found a modest delay in functional decline compared to placebo. However, no significant benefit was observed in cognitive outcomes, and concerns arose regarding increased all-cause mortality at high doses in some meta-analyses. Other studies have yielded mixed or negative results, with some showing no cognitive benefit in mild cognitive impairment or prevention settings.

Current major guidelines (such as those from the American Academy of Neurology and NICE) state that Vitamin E may have a very modest benefit for functional outcomes in established Alzheimer's dementia but do not recommend routine use given the potential risks and inconsistent evidence for cognitive improvement. In summary, there is some scientific evidence supporting Vitamin E's use in dementia, but the effect is limited and not robust, hence the low evidence rating.