Blueberries and other phytochemical-rich foods could help in increasing memory capacity by reversing age-related deficits in memory, according to a new rat study by UK researchers.
The study, conducted by researchers at the University of Reading and the Peninsula Medical School, has not yet been published but is expected to appear in the peer-reviewed journal Free Radical Biology and Medicine within the next few days.
After supplementing the diet of rats with blueberries over a 12-week period, the research team said that improvements in spatial working memory tasks emerged within three weeks and continued throughout the period of the study.
Three groups of adult male rats were used in the study. The first group comprised of 'young' rats, aged 6 months at the start of the testing period, while the remaining rats were all 18 months old and were randomly assigned to either an 'aged' group or an 'aged + blueberry-supplemented' group.
Those in the blueberry-supplemented group had powdered blueberries incorporated into the standard rat feed at a level of 2 per cent.
The researchers said that the two intervention diets used contained a defined and characterized amount of flavonoids (anthocyanins and flavanols) and were as far as possible macro- and micronutrient-matched. The two diets were isocaloric and matched for major antioxidant vitamins via the addition of corn starch and vitamin C (2 mg/kg) to the control diet.
The mean intake of flavonoids by blueberry-fed animals was approximately 10.5 mg/day (Anthocyanins: 6.68 mg/day; Flavanols: 3.85 mg/day).
Rats were tested in cross-maze apparatus, which they had to navigate in order to receive reward pellets. The animals were given a week's training in the apparatus before supplementation began in order to ensure that they ran reliably.
The researchers set up an alternate navigation/reward system, which involved rats having to make a choice as to which path to take in order to receive the pellets. For each trial, accuracy and time taken to make a choice were measured.
Old rats get sharp
Animals in the 'young' group were found to perform "extremely well and very consistently", scoring an average of 90 per cent correct on each test day.
The 'aged' animals were substantially impaired on this task compared to the young animals, with an average score of only 57 per cent correct.
Similarly, the 'aged + blueberry-supplemented' group showed an age-related deficit in performance compared to the 'young' animals at baseline achieving only 60 per cent accuracy of choice.
However, three weeks of blueberry supplementation produced a significant increase in performance in these animals, with accuracy rising to 83 per cent by testing in week three. This increase in performance accuracy was maintained throughout the remainder of the treatment period, said the researchers.
"This study not only adds science to the claim that eating blueberries are good for you, it also provides support to a diet-based approach that could potentially be used to increase memory capacity and performance in the future," said researcher Dr Matt Witterman, from the Institute of Biomedical and Clinical Science, Peninsula Medical School.
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 exert their effects on learning and memory by enhancing existing neuronal connections, improving cellular communications and stimulating neuronal regeneration, explained the researchers.
"Scientists have known of the potential health benefits of diets rich in fresh fruits for a long time. Our previous work had suggested that flavonoid compounds had some kind of effect on memory, but until now we had not known the potential mechanisms to account for this," said lead researcher Dr Jeremy Spencer, a lecturer in Molecular Nutrition at the University of Reading.
The research team said it plans to extend its findings further by investigating the effects of diets rich in flavonoids on people suffering from cognitive impairment and Alzheimer's disease.
Source: 'Blueberry-induced changes in spatial working memory correlate with changes in hippocampal CREB phosphorylation and BDNF levels'
To be published in Free Radical Biology and Medicine
Manuscript Number: FRBM-D-07-00468R2
Authors: Claire M Williams, PhD; Manal Abd El Mohsen, PhD; David Vauzour, PhD; Catarina Rendeiro, BSc; Laurie T Butler, PhD; Judi A Ellis, PhD; Matt Whiteman, PhD; Jeremy Paul Spencer, PhD