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NEW YORK (Reuters Health) April 18, 2007

by Amy Norton from Journal of Neuroscience

A fatty acid found in fish may help thwart the buildup of brain proteins linked to Alzheimer's disease, a study in mice suggests.

In Alzheimer's disease, lesions known as "plaques" and "tangles" form in the brain, due to the abnormal clumping of two proteins called beta-amyloid and tau. The mouse study found that a diet rich in the fatty acid DHA might interfere with this process.

DHA, short for docosahexaenoic acid, is a type of omega-3 fatty acid found mainly in fatty fish like salmon and mackerel, and to a lesser extent in seaweed, eggs, organ meats and DHA-fortified foods.

While the new findings come from studying mice, they complement studies in humans that have linked higher fish intake, as well as higher blood levels of DHA, to a lower risk of Alzheimer's disease.

Such research suggests that the animal findings might well translate to people, Dr. Frank LaFerla, the senior author on the new study, told Reuters Health.

He and his colleagues at the University of California at Irvine report their results in the Journal of Neuroscience. Several co-authors on the study are with Martek Biosciences Corp., a Maryland-based company that makes a DHA product used in a range of infant formulas, foods and supplements.

For their study, the researchers used mice genetically engineered to develop Alzheimer's-like plaques and tangles. At the age of 3 months, the animals were placed on one of four diets.

One diet mimicked the typical American diet, with low amounts of omega-3 fats and far higher levels of omega-6 fats, which are found in various vegetable oils, eggs and meat. The other three diets were rich in omega-3 fatty acids; one was supplemented with DHA only, while the other two had added DHA and omega-6 fats.

After 9 months, the study found, mice on the diet supplemented with DHA alone had lower levels of beta-amyloid and tau in their brain tissue than the animals in the other three groups.

The researchers also discovered that DHA may confer its benefit by lowering levels of an enzyme needed to generate beta-amyloid.

What's needed now, according to LaFerla, are clinical trials involving people with early-stage Alzheimer's to see whether DHA supplements can slow the progression of the disease. Martek has just launched such a study, he said.

SOURCE: Journal of Neuroscience, April 18, 2007.