Friday March 1 1:40 PM ET
More Evidence That Folate Cuts Alzheimer's Risk

By Merritt McKinney

NEW YORK (Reuters Health) - A new study in mice adds to growing evidence that low levels of folic acid may increase the risk of Alzheimer's disease.
The findings complement a recently published study linking elevated levels of the amino acid homocysteine with an increased risk of the degenerative disease, since folic acid is known to reduce homocysteine levels.
Assuming that the connection between low levels of folate and Alzheimer's holds true in human studies, eating more folate-rich foods may help stave off the disease, researchers say.
``Maintaining a sufficient daily intake of folic acid will keep brain cells healthy and may protect against Alzheimer's disease,'' Dr. Mark P. Mattson, of the National Institute on Aging Gerontology Research Center in Baltimore, Maryland, told Reuters Health. Mattson is the lead author of the folic acid study.
People with Alzheimer's tend to have below-average levels of folic acid, but the cause of this deficiency is uncertain. Low levels of folic acid could stem from the disease itself or may be caused by malnutrition.
To test the effects of folic acid on the brain, Mattson and his colleagues compared the effects of a diet low in folic acid. In mice genetically predisposed to develop Alzheimer's-related brain deposits, the low folic acid diet--which increased homocysteine levels more than 10-fold--led to considerable loss of neurons. In contrast, normal mice on the low-folate diet did not experience abnormal loss of brain cells.
Based on the findings, the researchers speculate that too little folic acid and too much homocysteine make neurons vulnerable to the development of Alzheimer's-related protein bits called amyloid beta peptides.
To get enough folic acid, he recommended eating plenty of folate-rich foods such as green, leafy vegetables, citrus fruits and juices, whole wheat bread and dried beans. An alternative approach is to take a daily supplement containing 400 micrograms of folic acid, according to Mattson, who is the lead author of the folic acid study. A report on the findings appears in the March 1st issue of the Journal of Neuroscience.
It may also be a good idea for people to find out what their homocysteine levels are, Mattson suggested.
Prior research has shown that elevated levels of homocysteine may increase the risk of heart disease and stroke, and there is some evidence that too much of the amino acid may increase the risk of dementia.
Diet has a major effect on homocysteine levels. Folic acid and other B vitamins may lower homocysteine levels by breaking down the amino acid. The benefits of lowering homocysteine levels have not been proven, however.
``People with elevated levels of homocysteine in their blood are at increased risk of Alzheimer's disease,'' according to Mattson. ``Because homocysteine levels can be decreased through folic acid supplementation and other dietary changes including reducing one's calorie intake, it is therefore useful to know one's homocysteine level.'' Blood homocysteine levels between 5 and 15 micromoles per liter are considered normal, noted Mattson, who added that it is ``desirable'' to keep homocysteine below 7 micromoles per liter.
Just as reducing cholesterol levels can lower the risk of cardiovascular disease, ``reducing levels of homocysteine can reduce risk of Alzheimer's disease,'' Mattson said.
SOURCE: Journal of Neuroscience 2002;22:1752-1762.
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