Do antioxidant vitamins impact prevalent causes of
References 11 to 14 present results concerning the impact of vitamin antioxidants on Alzheimer's Disease. Reference 11 discusses the effect of selegiline (a medication for Alzheimer's), alpha-tocopherol (vitamin E), or both as treatment for Alzheimer's. The study was double-blind, placebo controlled, and randomized - supposedly the most reliable type of study. 341 patients with moderately severe Alzheimer's received selegiline, vitamin E (200 IU per day), both, or a placebo, for a period of two years. In an initial analysis, no difference in the evolution of the disease was found. However in a more detailed analysis, they determined that the primary outcome - death, institutionalization, loss of ability to perfrom dily living activities, or severe dementia - was slower for the patients taking vitamin E or selegiline. These patients seemed to have seven more months before reaching the primary outcome. However later meta-studies on selegiline (Cochrane Database Syst Rev 2003;(1):CD000442) did not show any improvement, casting doubt on the vitamin E results as well.
Reference 12 - this study started with 5,400 participants, at least 55 years old, and dementia free. After an average follow up of 6 years, 197 participants developed dementia, of whom 146 had Alzheimer's. The study evaluated the intake of vitamins C and E from food using a questionnaire. The study found a small reduction in Alzheimer's incidence for people with the highest intake of vitamins from their diet - of the order of a risk reduction factor of 0.7. However, the Margin of Error includes a null result (no effect, risk reduction = 1.0), and therefore the statistical validity of any conclusion is questionable.
The study in reference 13 also evaluates the effect of vitamin E in foods. It has less participants than the study in reference 12, and so it does not provide a better estimate of any potential isk reduction factor. However, it has one noteworthy point: they observe that risk reduction due to vitamin E pertains only to individuals who have "APOE e4 allele" ( a specific genetic marker).
The last study we quote - reference 14 - examines the possibility that mid-life dietary intake of antioxidants impacts late-life dementia. 2,500 Japanese-American men, aged 45 to 68, with complete dietary data and who were dementia free at the start of the study, were evaluated for a period of up to 8 years. They conclude that intake of beta-carotene, flavonoids, and vitamins C and E have no impact on subsequent dementia!
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