DOES IT WORK?BACKGROUND: With the population ageing, more people are becoming concerned about memory loss – or what is more specifically called cognitive decline. A request was recently sent to this column to look at the evidence regarding blueberries and memory loss.
Memory loss can be due to the ageing process, or may be due to an underlying condition like Alzheimer’s disease, which is a leading cause of dementia. Research is being conducted to identify the various causes and risk factors for dementia. There is much interest in the potential of dietary factors to reduce cognitive decline and slow the onset of dementia.
Blueberries are closely related to cranberries and bilberries, all of which are members of the Vacciniumgenus. Bilberries are sometimes called blueberries, but true blueberries have a greenish white flesh whereas bilberries have a blue-purple flesh. The original "wild" blueberries come from Vaccinium angustifolium, a low-lying bush native to eastern Canada and northeastern US. A number of hybrids are now grown commercially in other regions.
Blueberries were primarily used as a nutritious fruit, high in fibre and vitamin C, but they were also used for a number of ailments. The dried leaves were used to treat sore throats and mouth inflammations. Recent interest in blueberries and memory loss has developed because they contain anthocyanins, which contribute to the red and purple colour of many fruits and flowers. Some are not absorbed when eaten, but other are and are powerful antioxidants.
EVIDENCE FROM STUDIES
The interest in diet and memory loss arises from large population surveys which found that higher consumption of fruits and vegetables is associated with better cognitive performance in the elderly and a lower risk of diseases that lead to dementia. However, such studies do not reveal whether dietary factors cause such effects, or whether diet is one of a number of contributing factors that help slow cognitive decline.
Because blueberries are high in antioxidants, which have beneficial health effects, they are being examined in many research projects. However, most have reached only the stage of animal testing. Anthocyanins pass into the brains of animals and can specifically enter those regions known to be important for memory. Some experiments have found that older animals fed blueberries performed better in memory tests.
What is believed to be the first study of blueberries in humans was published earlier this year. The study involved nine people with an average age of 76 years who were compared to seven people taking an artificial juice. Anyone diagnosed with no memory decline or having mild or more serious dementia was excluded from the study. Those involved had normal age-related forgetfulness, and thus belonged to a very specific group who were at the earliest stage of memory decline. Each person was asked to drink a commercial wild blueberry juice three times a day, consuming about 500ml daily. After three months, those drinking the blueberry juice had statistically significant improvements in memory compared to those drinking the placebo.
PROBLEMATIC ASPECTS
Blueberries are not known to cause problems. No adverse effects were reported in the above study, although blood glucose levels were reduced to a small extent. This could be beneficial for some, but anyone taking medication for diabetes should carefully monitor their sugar levels if they start consuming blueberries regularly.
RECOMMENDATIONS
Blueberries are a nutritious and safe food. They are being examined for a number of health benefits. However, research on their specific effects is at a very early stage. The authors of the above study noted that their research was preliminary and needed to be repeated with much larger numbers of people. For now, adding blueberries to a diet rich in fruits and vegetables is warranted. Whether blueberries alone will help prevent memory loss remains to be seen.
Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
