Do metals in our environment play a role in Alzheimer’s disease? A new study found that copper, found in drinking water carried by copper pipes and in foods like red meats, shellfish, nuts and many fruits and vegetables, may play a role in promoting the onset and progression of Alzheimer’s.
The findings are the latest to explore the possible role between metals like copper, iron and zinc and Alzheimer’s disease. But the relationship between metals and brain health is complex.
Copper, like many metals, plays a critical role in health. Along with iron, copper helps transport oxygen through the body. Copper also plays an important role in the communication between nerve cells, bone growth and hormone secretion, so it is important to get enough of the metal in your diet.
But the new study, published in the Proceedings of the National Academy of Sciences (PNAS), found that copper also may prevent the clearance of beta-amyloid, a protein that builds up in the brains of those with Alzheimer’s.
"It is clear that, over time, copper's cumulative effect is to impair the systems by which beta-amyloid is removed from the brain," said the study’s lead author, Rashid Deane, Ph.D., a research professor at the University of Rochester Medical Center Department of Neurosurgery. "This impairment is one of the key factors that cause the protein to accumulate in the brain and form the plaques that are the hallmark of Alzheimer's disease."
This is an interesting and potentially important study. However, it is unclear as to whether dietary copper -- too much or too little -- affects Alzheimer’s risk in humans and whether manipulation of dietary copper could prevent Alzheimer’s disease.
Over a three-month period, the researchers fed mice “very low levels of copper, equivalent to what people would consume in a normal diet," said Dr. Deane. They found that the copper made its way into the blood system and accumulated in the vessels that feed blood to the brain. There, the copper interfered with the enzyme that normally breaks down beta-amyloid in the brain. They also observed that in both mouse and human brain cells, copper stimulated activity in brain cells that increased the production of beta-amyloid, and promoted inflammation, which has also been linked to Alzheimer’s.
Because metals like copper are essential to so many other functions in the body, however, the researchers advise that these results must be interpreted with caution and that people must be careful not to eliminate copper from the diet.
"Copper is an essential metal, and it is clear that these effects are due to exposure over a long period of time," said Dr. Deane. "The key will be striking the right balance between too little and too much copper consumption. Right now we cannot say what the right level will be, but diet may ultimately play an important role in regulating this process."
This is an interesting speculation, but it remains unclear as to whether “balancing” dietary copper consumption will be important in preventing dementia.
Indeed, earlier studies have found that too little copper may be harmful to the brain. Research conducted at Keele University in the U.K. has found that copper, at healthy levels, may prevent beta-amyloid from forming senile plaques in the brain.
Other researchers have reported that a deficiency of zinc, a metal that helps make DNA and plays a role in short-term memory and learning, may likewise lead to cognitive problems. People with Alzheimer’s disease often have lower zinc levels than their peers, and some small studies have found that zinc supplements may improve brain function. Zinc is also thought to help keep copper levels at a healthy level.
Similarly, some research has found that an excess of iron can be toxic to the brain. But too little iron can lead to anemia, which has been tied to an increased risk of dementia.
More research is needed to explore the potential connections between metals and brain health. At this point, experts cannot deliver specific recommendations regarding measures to avoid getting too much – or too little – of metals in our diets in order to avoid Alzheimer’s disease.
During the 1960s and 1970s, for example, aluminum emerged as a possible suspect in Alzheimer’s disease. Many cautioned about exposure to aluminum through pots and pans, foil wrap and antiperspirants. Since then, studies have failed to confirm any role for aluminum in causing Alzheimer’s, and most experts now believe that aluminum does not play a role in the disease.
Source: Proceedings of the National Academy of Sciences.
July 2013, vol. 110 no. 36 pp. 14771–14776