A high-fat, copper-rich diet may increase the risk of cognitive decline in older adults, says a study by researchers at Rush University Medical Center in Chicago.

The study of 3,718 people, age 65 and older, found that a diet high in saturated fat and trans fats, combined with a high intake of copper, may be associated with an accelerated rate of decline in thinking, learning and memory abilities.

Food with high copper levels include organ meats (such as liver), shellfish, nuts, seeds, legumes, whole grains, potatoes, chocolate and some fruits. Copper pipes may also add trace amounts of the metal to drinking water.

The findings were published in the August issue of the journal Archives of Neurology.

The study participants' cognitive abilities were tested at the start of the study and again three years and six years later. They also provided information about their eating habits.