However, research is divided, with other studies suggesting copper may actually protect the brain. 

 

The latest study in Proceedings² of the National Academy of Sciences showed high levels of copper left the brain struggling to get rid of a protein thought to cause the dementia.

 

Copper is a vital part of our diet and necessary for a healthy body.

 

Tap water coming through copper pipes, red meat and shellfish as well as fruit and vegetables are all sources of dietary copper.

 

 

The study on mice, by a team at the University of Rochester in New York, suggested that copper interfered³ with the brain's shielding - the blood brain barrier. 

 

Mice that were fed more copper in their water had a greater build-up of the metal in the blood vessels⁴ in the brain. 

 

The team said this interfered with the way the barrier functioned and made it harder for the brain to get rid of a protein call beta amyloid.

 

One of the hallmarks of Alzheimer's disease is the formation of plaques⁵（斑块，瓷片） of amyloid（淀粉体） in the dying brain. 

 

Lead researcher Dr Rashid Deane said: "It is clear that, over time, copper's cumulative⁶ effect is to impair⁷ the systems by which amyloid beta is removed from the brain."

 

He told the BBC that copper also led to more protein being produced: "It's a double whammy（晦气，剧烈的打击） of increased production and decreased clearance⁸ of amyloid protein. 

 

"Copper is a very essential metal ion and you don't want a deficiency and many nutritious⁹ foods also contain copper."

 

However, he said taking supplements may be "going overboard a bit".

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