Alzheimer's disease may be prevented by supplementing with antioxidants. A distinguished group of medical researchers from four American universities has concluded that supplementation with vitamins C and E in combination is associated with a reduced prevalence and incidence of Alzheimer's disease (AD). Their study included almost 5,000 residents of Cache County aged 65 years or older. The prevalence (total number of AD cases at baseline) and the incidence (newly diagnosed cases per year of AD) over a 3-year follow-up period were determined and correlated with the reported use of multivitamins, vitamin B-complex supplements, and vitamins C and E.
The prevalence of AD in the segment of the study population not using any supplements was 4.9%. This compared to 0.9% among users of relatively high daily doses of vitamin C (500-1000 mg/day or more) and vitamin E (up to 1000 IU/day). After adjusting for known AD risk factors, including the presence of apolipoprotein E epsilon 4 alleles, the researchers conclude that supplementation with both vitamins C and E is associated with a 78% lower prevalence of AD. The use of vitamin C containing multivitamins in combination with vitamin E was associated with a 66% lower prevalence. The annual incidence of AD was 1.1% among participants not taking supplements as compared to 0.4% per year among those supplementing with vitamins C and E in combination. After adjusting for other risk factors the researchers conclude that supplementation with vitamins C and E is associated with a 64% lower incidence of AD. Supplementation with vitamin E and vitamin C containing multivitamins was associated with a 53% reduction in risk.
The researchers found no association between a reduced prevalence or incidence and the use of
multivitamins, vitamin B complex or vitamin C or E on their own. They conclude that vitamin C enhances the
beneficial effects of vitamin E by regenerating vitamin E after it has been oxidized in its effort to combat
oxidative stress. They also conclude that the amounts of vitamin C and vitamin E contained in multivitamins
(RDA levels) are insufficient to provide any meaningful protection against AD. They urge randomized
clinical trials to confirm their findings.