Ask the doctor: Can B vitamins help prevent dementia?

Q. Is it true that B vitamins can reduce my risk of Alzheimer's disease and other types of dementia?

A. The simple answer appears to be "probably not." But few things in medicine are simple. A century ago, we ate a lot more foods rich in B vitamins than we eat today. Diets low in B vitamins—particularly folic acid, vitamin B6, and vitamin B12—can raise blood levels of a natural chemical called homocysteine. This, in turn, can promote atherosclerosis of the arteries of the heart and brain—resulting in heart attacks, strokes, and dementia.