(Reviewed on 1/24/2005)
You probably heard about results of a study published in the February 14, 2002 issue of the New England Journal of Medicine which showed that people with high blood levels of homocysteine have twice the normal risk of developing Alzheimer's disease. Homocysteine is a toxic amino acid, a breakdown product of protein metabolism,that has been linked to heart attacks and strokes. Blood levels of homocysteine tend to be higher in people whose diets are high in animal protein and low in fruits and leafy vegetables. Fruits and leafy vegetables provide folic acid and other B vitamins that help the body get rid of homocysteine.
This study is interesting: it doesn't prove that diet causes Alzheimer's disease, but it amplifies earlier knowledge that people with the disease have high homocysteine levels. The earlier studies didn't reveal whether the disease was responsible for the high homocysteine levels or whether the high levels were there first and might, therefore, be a cause of the disease. This study looked at 1,092 men and women whose homocysteine levels were monitored for eight years. All were healthy at the outset but by the year 2000, 111 had dementia including 83 with Alzheimer's disease. Those study participants whose homocysteine levels were highest - above 14 micromoles per liter of blood - had nearly twice the risk of Alzheimer's than those with lower homocysteine levels.
The researchers, a team from Boston University and Tufts University, aren't advising people to take B vitamins to prevent Alzheimer's because there haven't yet been studies proving that this strategy works. But we know for sure that a diet high in fruits and vegetables helps keep homocysteine levels low and thus protects against heart disease and strokes. I personally recommend taking a multivitamin that gives you 400 micrograms of folic acid in addition to what you might get from your diet (Some people might absorb this vitamin better in supplement form, and I consider this good insurance.)
Incidentally, results of another study reported that the more often you challenge your mind, the lower your risk of developing Alzheimer's disease. The study, published in the February 13, 2002 issue of the Journal of the American Medical Association found that people who participate daily in such activities as reading, listening to the radio, watching television, playing cards, checkers and other games were at lower risk. More research is needed to determine which types of mental activities are most protective.
Andrew Weil, M.D.