Amino-Acid Tied to Alzheimer's Risk

Source: Tufts University
March 27, 2002 (Reviewed: March 7, 2004)

Heart-health conscious consumers have likely heard about homocysteine -an amino-acid that, at higher-than-normal levels in the bloodstream, can damage blood vessels. New research published in The New England Journal of Medicine speculates that high homocysteine can also damage the delicate blood vessels in the brain, setting the stage for the development of dementia.

A closer look at the data

Boston researchers analyzed information gathered on more than a thousand older participants of the long-running Framingham Study. They looked for a link between blood homocysteine measurements collected in 1990 and the development of dementia in the decade that followed.

The researchers found that the risk of dementia rose with increasing homocysteine levels. Participants with high homocysteine levels -- greater than 14 micromoles/liter -- were almost twice as likely as others in the study to develop Alzheimer's disease. This association held even after the researchers accounted for other factors -- like age and blood pressure --known to affect disease risk.

What's the connection?

Doctors already know that high homocysteine levels increase the risk of stroke, which, in turn, increases the chance of developing Alzheimer's disease. Supplemental doses of certain B vitamins -- folic acid, B12, and B6 -- can lower blood homocysteine levels by helping to convert it to another, more useful amino-acid. Homocysteine levels naturally rise with age, though, and scientists are not yet sure if B vitamin supplements can help seniors keep their homocysteine levels consistently low enough to sidestep the accumulating blood vessel damage that likely contributes to the development of Alzheimer's disease.

But even with some questions still to be answered, the researchers note that homocysteine levels in the Framingham Study participants have steadily dropped in the five years since the U.S. began fortifying grain foods with folic acid. It's too early to tell if that has made a significant dent in the incidence of dementia in this aging population, but scientists are focusing on the homocysteine-lowering potential of the B vitamins, especially folic acid.

Advice to consumers

Homocysteine testing isn't routinely included in most health check-ups, although some physicians believe that, along with cholesterol testing, it's a good way to assess cardiovascular health.

What about vitamin supplements? It's not yet clear if more B vitamins now would lead to less risk of dementia later on, and it's also not known how much of each vitamin would be needed to provide maximum benefit. If you diet is lacking in variety, though, or if you do not eat many folic acid-fortified grain foods, you may want to consider adding a multivitamin that includes 100% of the RDA of folic acid, B6, and B12 to your daily routine. It can't hurt, and it may help keep harmfully high levels of homocysteine in check.

Source

• Plasma homocysteine as a risk factor for dementia and Alzheimer's disease. S. Seshadri, A. Beiser, J. Selhub,  et al., N Eng J Med, 2002, vol. 346, pp. 476--483

Related Links
Risk Factors for Alzheimer's
Oxidative Damage, Part IV: Does Your Multivitamin Protect You?
Folate Part of a Heart Healthy Diet
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