A study of 16,010 female nurses in the US suggests that eating greater amounts of blueberries and strawberries is associated with a slower rate of cognitive decline. The study is published on 26 April in the journal Annals of Neurology.
The researchers used data from the Nurses’ Health Study, a long-term study that has been following more than 100,000 female nurses since 1976. Every two years, the nurses completed questionnaires on their lifestyle and health and every four years since 1980 they have also recorded details of the types of food they eat.
Every two years between 1995 and 2001, 16,010 of the volunteers from the Nurses’ Health Study who were over the age of 70 were asked to complete telephone-based memory and thinking tests. The scientists have now used this information to look for relationships between the nurses’ performance on the cognitive tests and the types of food they eat.
The study shows that nurses who reported eating more than one serving of blueberries a week showed a slower decline in memory and thinking skills than those who reported eating less than one portion a month. Similarly, those nurses who reported eating more than two portions of strawberries a week showed a slower rate of cognitive decline than those who ate less than one serving a month.
Strawberries and blueberries are rich in a group of naturally occurring antioxidants called flavonoids, which the scientists suggest may help to delay cognitive aging by protecting brain cells from chemical stress which can build up as we age.
Dr Eric Karran, Director of Research at Alzheimer’s Research UK, the UK’s leading dementia research charity, said: “Population studies like this can provide useful clues about the effects of lifestyle and diet on cognition, but we must be sensible when interpreting the results. The study suggests a link between eating berries and slower cognitive decline, but there could be many factors at play.
“It is not possible to say whether the increased consumption of berries resulted in an increased, beneficial level of flavonoid antioxidants in the brain. Further research will be needed to conclude whether antioxidants in berries are beneficial in the brain and we can’t assume that simply eating berries could protect against cognitive aging or dementia.
“Understanding the factors that affect our memory and thinking as we age can help us to understand possible risk factors for dementia. Previous evidence has shown that eating fruit as part of a healthy diet in midlife could help to reduce our risk of dementia and so eating a healthy balanced diet is something we should all be thinking about. With 820,000 people in the UK living with dementia, there is an urgent need to understand more about how to reduce the risk.”