Among older adults whose diets are high in saturated and trans fats, a high intake of copper may be associated with an accelerated rate of decline in thinking, learning and memory abilities, according to a report in the August issue of Archives of Neurology, one of the JAMA/Archives journals.

Although copper, zinc and iron are essential for brain development and function, an imbalance of these metals may play a role in the development of brain plaques associated with Alzheimer's disease. Previous studies have also linked fat intake, especially that of saturated and trans fats, to Alzheimer's disease and other forms of cognitive difficulties, according to background information in the article. One recent animal study found that the consumption of copper in drinking water could amplify the degenerative effects of a high-fat diet on rabbit brains.

Martha Clare Morris, Sc.D., Rush University Medical Center, Chicago, and colleagues assessed the connection between dietary fat and dietary copper intake in 3,718 Chicago residents age 65 years and older. Participants underwent cognitive testing at the beginning of the study, after three years and after six years. An average of one year after the study began, they filled out a questionnaire about their diets. The dietary recommended allowance of copper for adults is .9 milligrams per day. Organ meats, such as liver, and shellfish are the foods with the highest copper levels, followed by nuts, seeds, legumes, whole grains, potatoes, chocolate and some fruits. Copper pipes may also add trace amounts of the metal to drinking water.

Cognitive abilities declined in all participants as they aged. Overall, copper intake was not associated with the rate of this decline. However, among the 604 individuals (16.2 percent of the study group) who consumed the most saturated and trans fats, cognitive function deteriorated more rapidly with the more copper they had in their diets. "The increase in rate for the high-fat consumers whose total copper intake was in the top 20 percent (greater than or equal to 1.6 milligrams per day) was equivalent to 19 more years of age," the authors write.

Other metals assessed in this study, iron and zinc, did not show any effects on cognitive decline in interaction with a high-fat diet. Previous studies have found higher levels of copper in the blood of patients with Alzheimer's disease, and medications that bind with copper to block its effects have shown promise treating patients with the condition.