Eating blueberries and strawberries may stave off mental decline in later life, claim researchers.
They found brain ageing could be delayed by up to two and a half years in elderly women regularly eating high amounts of the berries.
The findings come from an ongoing study of nurses which involves only women, but may also apply to men.
Experts believe the benefits are derived from the high content of flavonoids in berry fruits, antioxidant compounds found in plants which can protect against a wide range of diseases.
The US research team used data from the Nurses’ Health Study, involving 121,700 female, registered nurses between the ages of 30 and 55 who completed health and lifestyle questionnaires beginning in 1976.
Since 1980 participants were surveyed every four years regarding their frequency of food consumption.
Between 1995 and 2001, cognitive function was measured in 16,010 women over the age of 70 years, at 2-year intervals, says a report in the Annals of Neurology journal.
The findings suggest increased consumption of blueberries and strawberries slows cognitive decline in older women.
Those who had higher berry intake delayed cognitive aging by up to 2.5 years.
The authors warn they cannot rule out the possibility that women who eat more berries also have other healthy habits, such as exercising more, which may play a part in the overall findings.
However, they found a greater intake of anthocyanidins and total flavonoids was also associated with less cognitive deterioration.
Experts believe that stress and inflammation contribute to cognitive impairment and that increasing consumption of flavonoids could mitigate the harmful effects.
Brain cells are particularly sensitive to free radicals, destructive groups of atoms made as a by-product of metabolism that can damage cell membranes and DNA.
Antioxidants help to neutralise free radicals, Dr Elizabeth Devore with Brigham and Women’s Hospital and Harvard Medical School in Boston, Massachusetts, said ‘Our study examined whether greater intake of berries could slow rates of cognitive decline.
‘We provide the first epidemiologic evidence that berries may slow progression of cognitive decline in elderly women.
‘Our findings have significant public health implications as increasing berry intake is a fairly simple dietary modification to test cognition protection in older adults.’
Derek Hill, CEO of IXICO and Professor of Medical Imaging Sciences, University College London, said: ‘Later this year, two major drug trials targeting the proteins in the brain associated with Alzheimer’s Disease will announce their results. Many experts fear these drugs will be added to the long list of potential dementia treatments that fail to demonstrate conclusively that they slow cognitive decline.
‘This latest research suggesting that a diet high on berries can slow cognitive decline in the elderly population is therefore especially welcome.
‘It is a large and well-designed study that significantly strengthens the evidence that changes to diet may be able to delay onset of dementia symptoms.
‘This suggests that we can take further steps to tackling the scourge of dementia in society while we await the arrival of effective new medicines.’
Dr Eric Karran, Director of Research at Alzheimer’s Research UK, 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.
‘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.’
Carol Brayne, Professor of Public Health Medicine, University of Cambridge, said: ‘Broccoli, blueberries, Mediterranean diet, Sudoku…..it is very difficult indeed to be sure that this is not residual confounding as these kinds of dietary patterns are associated with many other positive attributes, which themselves are associated with healthier ageing.
‘Blueberries have been of interest for many years and it’s certainly worth further investigation, but for definitive evidence we have to await well designed trials as this is another observational study.’
The range of consumption in the study was women eating less than one serving of blueberries a month, between one and 3 servings a month and more than one serving a week, and from less than one serving of strawberries a week to more than two a week.
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