MUNCHING a bowl of blueberries for breakfast can stop you flagging in the afternoon, a new study shows. Researchers found that a large helping of the fruit - described by some as natures 'superfood - boosts concentration and memory up to five hours later. In tests, volunteers who drank a blueberry smoothie in the morning did much better at mental tasks in the mid afternoon than people who had an alternative drink. British scientists who made the discovery believe the antioxidants in blueberries stimulate the flow of blood and oxygen to the brain - and keep the mind fresh. The finding means people could use blueberries and other fruit rich in anti-oxidants to improve their chances during exams or on long, difficult days at work. Dr Jeremy Spencer of Reading University, who carried out the study, said: 'After one hour there was little difference in the attention tests. 'But after five hours people who didnt have the blueberry smoothie saw their performance fall by 15 to 20 per cent. Blueberries are bursting with vitamins C and E. Nutritionists say they are one of the richest sources of cancer-fighting antioxidant called flavonoids, which are also found in green tea, wine, grapes and cocoa. Past studies have shown that flavonoids can protect against degenerative diseases and even help people lose weight. In the latest study - presented yesterday (THU) at the British Science Festival in Surrey University, Guildford - Dr Spencer recruited 40 volunteers aged 18 to 30 and 40 volunteers aged over 65. On the first day of the experiment, they were given a standard breakfast of toast and marmalade, followed by a mid morning smoothie made from 200g of blueberries. An hour after the smoothie they carried out 45 minutes of computer based mental tests. The tests measured their short term working memory and their concentration. The tests were repeated five hours after the smoothie. DM Two weeks later the volunteers carried out the same experiment - but this time drank a 'control smoothie containing the same amount of sugars and calories but with no blueberries. In the tests, carried out an hour after the smoothie, the presence of blueberries in the smoothie made no difference to the volunteers performance. But as the day wore on, the volunteers who didnt have the blueberries saw their performance and concentration slipping. When they were tested after five hours their performance was significantly worse. In contrast, the volunteers who had the blueberry drink saw no decline in their mental powers, the scientists said. Dr Spencer said the brain boosting power was not unique to blueberries. 'From our studies, other foods containing flavonoids - such as strawberries , cocoa and raspberries - would be similar, he said. 'Its not right to single out blueberries. The Reading researchers believe that flavonoids in berries activate an enzyme in the body called Enos which increases the flow of blood and oxygen to the brain. Without this boost, brains become tired as the day goes on and find it harder to concentrate. Blueberries contain a cocktail of anti-oxidants including anthocyanins, proanthocyanidins, resveratrol and tannins. The fruit are thought to protect against cancer and heart disease, and may even prevent dementia.