NEW YORK: A chemical found in chocolate, tea, grapes and blueberries may boost memory by improving blood flow in the brain especially in combination with exercise, latest research suggests.

The study, published in the American Journal of Neuroscience, was conducted on mice. The scientists now plan to study the effects of the chemical epicatechin on memory and brain blood flow in aged animals and then humans, combined with mild exercise.

The food chemical epicatechin is one of a group of chemicals known as flavanols found in certain food items including chocolate, tea, grapes and blueberries. Earlier studies have already shown that the antioxidant compound flavanol could help improve cardiovascular health.

Now the researchers, led by Henriette van Praag, working with chocolate firm Mars, compared mice that were fed a normal diet with those that were fed a diet supplemented with epicatechin.

Half the mice in each group were allowed to run on a wheel for two hours each day and were trained to find a platform hidden in a pool of water, a month later.

Those mice that exercised and ate the epicatechin diet remembered the location of the platform longer than the other mice. The epicatechin-fed mice who did not exercise also showed enhanced memory, but to a lesser degree. The mice on the special diet appeared to have greater blood vessel growth in certain parts of their brain, along with more mature brain nerve cells, the online edition of BBC News reported.

"This is important because it identifies a single natural chemical with memory-enhancing effects, suggesting it may be possible to optimise brain function by combining exercise and dietary supplementation," Mark Mattson, a doctor at the US National Institute on Ageing, said.

However, nutritionists warned chocolate is high in fat and sugar, which may undo any potential benefits. They recommended a diet rich in fruit and vegetables, with perhaps a small amount of chocolate.