Scientists at the Salk Institute in California say that a chemical found in chocolate improves the memory of mice.
The chemical epicatechin is also found in cocoa, tea, grapes and blueberries and the researchers believe it improves the blood flow in the brain especially in combination with extra exercise.
The study is not the first to suggest a link between 'flavanol' chemicals in certain foods and health benefits; other studies have also suggested that cardiovascular health can be improved by including them in the diet.
The researchers, led by Dr. Henriette van Praag, worked with the chocolate company Mars and compared mice fed a typical diet with those 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 then, a month later, were trained to find a platform hidden in a pool of water.
The researchers found that those that both 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 researchers say 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 scientists say epicatechin can improve the memory of mice and the research could lead to further tests to see if epicatechin also works on humans.
Nutritionists however caution that chocolate should be eaten in small amounts as it is also high in fat and sugar, which may well undermine any potential benefits.
They recommend people eat a diet rich in fruit and vegetables, with just a small amount of chocolate.
Van Praag and her team say the study is good news for those researching neurodegenerative diseases such as Alzheimer's and the cognitive disorders related to aging.
Dr. Praag says the next step will be to study the effects of epicatechin on memory and brain blood flow in older animals and then humans, in combination with mild exercise.
The study is published in the Journal of Neuroscience.