Older adults who consume orange and grapefruit every day can lower the risk of dementia by 23%, finds a study.

Researchers from Tohuku University in Japan have found that daily intake of any citrus fruits such as oranges, grapefruits, lemons or limes can cut the chances of developing the incurable brain condition by almost a quarter.

The findings suggested that the citric acid contains a chemical nobiletin, which in animal tests has shown to slow or reverse impairment of memory. The team analysed more than 13,000 older adults for up to seven years to see how many developed dementia.

Rates of dementia among those eating citrus fruits at least once a day were significantly lower than in volunteers having them less than twice a week.

"Some biological studies have indicated citrus may have preventive effects against cognitive impairment," the researchers stated."But no study has examined the relation between citrus consumption and rates of dementia. Our findings suggest frequent consumption is linked with a lower risk of dementia," they concluded.