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A diet high in saturated and trans fats as well as copper can lead to an accelerated rate of mental decline in the elderly, according to a U.S. study.

Previous studies have already shown that artery-clogging saturated and trans fats are bad for your heart. The new research suggests how copper might interact with these fats to foster the development of harmful brain plaques associated with Alzheimer's disease.

"A diet that is high in saturated and trans fat increases blood cholesterol levels. In the brain, high cholesterol leads to increased levels of amyloid, an abnormal protein," explained Martha Clare Morris, who led the research team at Rush University Medical Center in Chicago.

"Copper reacts with amyloid causing it to bind, and perhaps prevent its clearance from the brain," she said in an e-mail interview. As a result, "the accumulated amyloid forms into plaques" which clog up the normal processes of the brain.

Copper is found in a wide range of foods. Organ meats (such as liver) and shellfish are the foods with the highest levels, followed by nuts, seeds, legumes, whole grains, potatoes, chocolate and certain fruits (pears, apricots and tomatoes).

The researchers aren't suggesting you should shun these foods; in fact, many of them contribute to a healthy, balanced diet. The typical adult needs 0.9 milligrams of copper a day.

Instead, just cut back on the bad fats. "At this point in the research, the recommendation should be to avoid a diet high in saturated and trans fats," said Dr. Morris, whose study is published in the journal Archives of Neurology.

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