Vitamin E has been promoted as a natural preventive or cure for several ills widespread among Americans such as heart disease, some types of cancer, and Alzheimer's disease. Unfortunately, as we ve noted before, when studied in randomized, placebo-controlled clinical trials, vitamin E does not live up to its reputation (see http://www.acsh.org/news/newsID.446/news_detail.asp and http://www.acsh.org/factsfears/newsID.524/news_detail.asp ). The latest blow came in the results of a study published in the April 14 New England Journal of Medicine.
Researchers at several clinical centers studied 769 older people (age range 55-90 years) with mild cognitive impairment. Their responses to supplementation with high doses of vitamin E (2000 IU/day) and/or the drug donepezil (Aricept), or placebo were assessed. This randomized, double-blind study was designed to assess whether either supplement or drug could slow the progression of cognitive impairment to Alzheimer's disease.
After three years of treatment, neither the vitamin E nor donepezil-treated participants had been helped by their respective regimens. That is, they developed Alzheimer's disease at rates similar to those experienced by subjects given inactive placebos. (After one year, the patients given donepezil did seem to show a slowing of progression, but this difference disappeared as the study continued).
A common argument for use of vitamins for disease prevention or treatment (as opposed to synthetic drugs) is that they are "natural" and that since a little is good, a lot "can't hurt." While the current study did not look for evidence of harm from use of high vitamin E doses, other studies have done so and found them. For example, the recent HOPE trial found an increased risk of heart failure among patients taking 400 IU of vitamin E over a 7 year period. Further, vitamin E did not reduce the incidence of cancer or reduce the deaths from cancer in this study. (1)
The take-home message is clear: vitamins are essential nutrients and we must have them in adequate amounts for good health. Thus far, however, it is clear that vitamins are not, as is often implied, superior to pharmaceuticals for preventing or treating disease. ACSH advises consumers to be wary of excessive claims for such "natural" treatments: we should demand the same rigorous demonstration of efficacy for high-dose vitamin regimens as we do for pharmaceutical agents.
For more information about Alzheimer s disease, see the ACSH publication at: http://www.acsh.org/publications/pubID.280/pub_detail.asp .
(1) HOPE and HOPE-TOO Trial Investigators. (2005). Effects of the long-term use of vitamin E supplementation on cardiovascular events and cancer: A randomized controlled trial. JAMA, 293, 1338-1347.