High dietary copper intake markedly accelerated the rate of cognitive decline in people whose diet was also high in saturated and trans fats, reported Dr. Martha Clare Morris of Rush University Medical Center, Chicago, and her associates.
In their analysis of data on 3,718 community residents who were enrolled in the Chicago Health and Aging Project (CHAP), the increase in the rate of cognitive decline “for the high-fat consumers whose total copper intake was in the top 20% (more than 1.6 mg/day) was equivalent to 19 more years of age.” This is “an extraordinarily large estimate of effect,” the researchers said.
Previous studies using data from the CHAP study population had shown that subjects who consumed high levels of saturated or trans fats had two to three times the risk of incident Alzheimer's disease and more rapid cognitive decline than people whose diets were lower in those fats. After noting the results of animal and other human studies that suggested dietary copper may induce the accumulation of amyloid-beta in the brain and cause memory deficits, Dr. Morris and her associates looked at the data on copper intake in the CHAP population.
The subjects were 65 years and older at entry into the study, and were assessed using four different measures of cognitive function at 3- and 6-year follow-up. Among the 604 subjects (16% of the entire cohort) who consumed a diet high in saturated and trans fats, there was a 143% increase in the rate of cognitive decline for those in the highest quintile of copper intake (median 2.75 mg/day), compared with those in the lowest quintile (median 0.88 mg/day).
In contrast, there was no association between copper intake and cognitive decline in subjects who had lower consumption of saturated and trans fats, the investigators said (Arch. Neurol. 2006;63:1085–8).
Copper, zinc, and iron are essential for normal brain function, but the “dyshomeostasis of these metals is thought to play a central role in the formation and neurotoxicity of amyloid-beta and neurofibrillary tangles,” they noted.
In this study, the link with accelerated cognitive decline was specific to copper. Zinc and iron levels showed no interactions with dietary fats.
In a further analysis of data on the subset of 602 subjects who took vitamin supplements containing copper, high copper intake again was associated with faster cognitive decline, but only in those whose diets were high in saturated and trans fats. These results “must be viewed with caution” because the study design was observational rather than prospective, and “the supporting evidence on this topic is limited,” Dr. Morris and her associates said.