What Vitamin Dose Prevents Alzheimers?

Q. I just heard on the news that large doses of vitamins C and E have been shown to help stave off Alzheimer’s in older people. Do you know anything about this? And if this is true, what constitutes a large dose? Apparently it is more than what is supplied in a regular daily multi-vitamin.
A. Scientists studied nearly 5,000 older people in Cache County, Utah, and determined that those who took extra vitamin C and E were much less likely to develop Alzheimer’s disease (Arch Neurol, Jan. 2004). It may have been the combination effect of the higher doses (over 400 IU of vitamin E and 500 mg of vitamin C) since ordinary multi-vitamin use did not provide such protection.