A daily drink of about 500 mL of blueberry juice was associated with improved learning and word list recall, as well as a suggestion of reduced depressive symptoms, according to findings published in the Journal of Agricultural and Food Chemistry.
The study is said to be the first human trial to assess the potential benefits of blueberries on brain function in older adults with increased risk for dementia and Alzheimer’s.
Alzheimer's disease is the most common form of dementia and currently affects over 13 million people worldwide. The direct and indirect cost of Alzheimer care is over $100bn (€ 81bn) in the US alone. The direct cost of Alzheimer care in the UK was estimated at £15bn (€ 22bn).
“These preliminary memory findings are encouraging and suggest that consistent supplementation with blueberries may offer an approach to forestall or mitigate neurodegeneration,” wrote the researchers, led by Robert Krikorian from the University of Cincinnati Academic Health Center.
“Interpretation of our findings should be tempered because of the relatively small sample size and the absence of a blueberry-specific control, although comparison with the analogous placebo beverage data provides some assurance that the observed changes in memory performance were not attributable to practice effects,” they added.
Berries are booming
Blueberry consumption has previously been linked to reduced risk of Alzheimer’s, with reports in 2003 leading to a boom in sales in the UK, going from £10.3m (€14.9m) in 2003 to almost £40m (€58m) in 2005, according to UK supplier BerryWorld.
The beneficial effects of the blueberries are thought to be linked to their flavonoid content - in particular anthocyanins and flavanols. The exact way in which flavonoids affect the brain are unknown, but they have previously been shown to cross the blood brain barrier after dietary intake.
It is believed that they may exert their effects on learning and memory by enhancing existing neuronal connections, improving cellular communications and stimulating neuronal regeneration.
Krikorian and his co-workers recruited nine older people with an average age of 76.2 and an average educational level of 15.6 years. Subjects were assigned to receive a daily dose of blueberry juice equivalent to between 6 and 9 mL per kilogram of body weight per day. The juice used in the study was provided by the Wild Blueberry Association of North America.
Results showed significant improvements in improved learning and word list recall. There was also a trend towards reduced depressive symptoms and lower glucose levels. Krikorian and his co-workers added that it would be interesting in future studies to examine if changes in cognitive function are associated with metabolic improvements.
“Replication of the findings in a larger, controlled trial will be important to corroborate and amplify these data,” wrote the researchers. “On balance, this initial study establishes a basis for further human research of blueberry supplementation as a preventive intervention with respect to cognitive aging,” they concluded.
The other researchers were affiliated with Agriculture and Agri-Food Canada and the USDA Human Nutrition Research Center on Aging and Tufts University.
Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, doi: 10.1021/jf9029332
“Blueberry Supplementation Improves Memory in Older Adults”
Authors: R. Krikorian, M.D. Shidler, T.A. Nash, W. Kalt, M.R. Vinqvist-Tymchuk, B. Shukitt-Hale, J.A. Joseph