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Browning meat in the oven, grill or frying pan produces chemicals which may increase the risk of developing dementia, US researchers suggest.

Advanced glycation end (AGE) products have been linked to diseases such as type-2 diabetes.

Mice fed a high-AGEs diet had a build-up of dangerous proteins in the brain and impaired cognitive function.

Experts said the results were "compelling" but did not provide "definitive answers".

AGEs are formed when proteins or fats react with sugar. This can happen naturally and during the cooking process.

Researchers at the Icahn school of medicine at Mount Sinai, in New York, tested the effect of AGEs on mice and people.

The animal experiments, published in Proceedings of the National Academy of Sciences, showed that a diet rich in AGEs affects the chemistry of the brain.

It leads to a build-up of defective beta amyloid protein - a hallmark of Alzheimer's disease. The mice eating a low-AGEs diet were able to prevent the production of damaged amyloid.

This subject has so far not been well studied in people, and we don't yet know whether the amount of AGEs in our diet might affect our risk of dementia Dr Simon Ridley, Alzheimer's Research UK

The mice performed less well in physical and thinking tasks after their AGEs-rich diet.

A short-term analysis of people over 60 suggested a link between high levels of AGEs in the blood and cognitive decline.

'Effective treatment'

The study concluded: "We report that age-related dementia may be causally linked to high levels of food advanced glycation end products.

"Importantly, reduction of food-derived AGEs is feasible and may provide an effective treatment strategy."

Derek Hill, a professor of medical imaging sciences at University College London, commented: "The results are compelling.

"Because cures for Alzheimer's disease remain a distant hope, efforts to prevent it are extremely important, but this study should be seen as encouraging further work, rather than as providing definitive answers.

"But it is grounds for optimism - this paper adds to the body of evidence suggesting that using preventative strategies might reduce the prevalence of Alzheimer's disease and other dementias in society and that could have very positive impact on us all."

Dr Simon Ridley, from the charity Alzheimer's Research UK, said: "Diabetes has previously been linked to an increased risk of dementia, and this small study provides some new insight into some of the possible molecular processes that may link the two conditions.

"It's important to note that the people in this study did not have dementia. This subject has so far not been well studied in people, and we don't yet know whether the amount of AGEs in our diet might affect our risk of dementia."