Drinking orange juice every day could help improve the brain power of elderly people, researchers claim.

And it takes less than two months to show marked improvements in memory, speech and reaction times, according to a study.

Scientists think the results are down to chemicals called flavonoids - a natural substance which occurs in high levels in oranges. Research has suggested that flavonoids may improve memory through the activation of signalling pathways in the hippocampus, a part of the brain that is associated with learning and storing information. A research team from Reading University asked 37 healthy volunteers to drink 500ml - nearly a pint - of orange juice every day for eight weeks.

The participants - 24 women and 13 men aged 60 to 81 - saw significant improvements in their brain function, the researchers found.

Their memory, reaction time and verbal fluency was measured at the beginning and end of the experiment, and each participant given an overall score known as 'global cognitive function'.

Their scores improved 8 percent - a remarkable improvement in less than two months. The researchers said they do not necessarily recommend that people drink an entire pint of orange juice every day. But they suggested that constituents of orange juice could play an important role in providing brain-boosting nutrients.

Study author Dr Daniel Lamport, from Reading's school of psychology, said, "The population is ageing rapidly across the world. Estimates suggest that the number of persons aged 60 or over could triple by 2100. It's therefore imperative that we explore simple, cost-effective ways to improve cognitive function in old age."

Dr Lamport, whose findings are published in the American Journal of Clinical Nutrition, said that if sustained, the mental improvement could make a substantial difference over the course of a lifetime. One of the tests his team carried out was asking the participants to memorise a list of 15 words which was recalled immediately and after a 30 minute delay.

The 8 percent improvement equated to remembering one more word from the shopping list at the end of the experiment, compared to the beginning.

Orange juice is a major source of a group of naturally-occurring plant phytochemicals known as flavonoids. Other flavonoid-rich foods such as blueberries are beneficial for cognition, separate studies have found. Recent research has suggested that flavonoids may improve memory through the activation of signalling pathways in the hippocampus, a part of the brain that is associated with learning and storing information.

Scientists are not exactly sure how this works, but they suspect the chemicals may improve blood flow, protect neurons against oxidative damage and increasing the efficiency with which neurons transmit signals. The new study is thought to be the first to show that regularly drinking orange juice flavonoids could have a positive effect on elderly people's brain power.

Dr Lamport said, "Small, easily administered changes to the daily diet, such as eating more flavonoid-rich fruits and vegetables, have the potential to substantially benefit brain health. We know that people find it difficult to sustain big changes to their diet but simple alterations are much easier to maintain permanently. More research on the positive effects of flavonoids on cognition is still needed. However, this is an important discovery which strengthens the growing body of evidence that flavonoid rich foodstuffs could play a big role in tackling cognition decline in old age."