Blueberries May Reverse
Age-Related Mental Decline
Cognitive performance declines naturally with age, but new results published in Nutrition indicate that for elderly rats, one month's supplementation with blueberries was associated with an improvement in the memory scores, as measured in a maze.
In addition, data showed that two months of consuming the blueberry-enriched diet was associated with a prolongation of the benefits after the diet was stopped, and the performance of the aging rats was similar to that of younger rats.
"Therefore, one-, two- and four-month diets substantially reversed the age-related object memory impairment found in 19-month-old rats," wrote researchers from the University of Houston and Tufts University U.S. Department of Agriculture Human Nutrition Research Center on Aging. "This illustrates a surprisingly prompt and powerful effect of an antioxidant dietary intervention," they added.
Blueberry consumption has previously been linked to reduced risk of Alzheimer's, and the beneficial effects of the blueberries are thought to be associated with their flavonoid content––in particular anthocyanins and flavanols. The exact way in which flavonoids affect the brain is 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.
Earlier this year, researchers from the University of Cincinnati Academic Health Center reported that 12 weeks of consuming a daily drink of about 500 ml of blueberry juice was associated with improved learning and word list recall (Journal of Agricultural and Food Chemistry 58:3996-4000, 2010). The study was 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.
The new study, led by Houston's David Malin, PhD, examined the effects of one or two months of consuming a blueberry-enriched diet in aging Fischer-344 rats.
Results showed that animals receiving the blueberry diet performed better than animals not receiving a berry-enriched diet and that two months of supplementation resulted in a maintenance of the improved performance after the supplementation period ended. No such effects were observed in the one-month group, said the researchers.
The researchers noted, "One possible explanation [for this observation] is a 'threshold hypothesis.' This hypothesis assumes there is a threshold concentration of antioxidants, particularly longer-lasting fat-soluble antioxidants, needed to maintain alleviation of memory impairment.
"The two-month diet might have produced a larger surplus of antioxidant nutrients over the threshold, whereas the one-month diet might have produced only a scant surplus above the threshold. Then, as the antioxidant nutrients are metabolized, the one-month diet might soon lose its ability to prevent memory impairment, whereas this loss of effectiveness might hypothetically take much longer after the two-month diet," they added.
Furthermore, rats on the blueberry diet increased their memory scores, while the control animals displayed a decline in memory scores.
"The present study is encouraging in terms of potential human application," wrote Dr. Malin and his co-workers. "First, the present results suggest that even a relatively brief blueberry diet might produce measurable benefits. Second, the benefits of several months of diet might be maintained for a considerable period after the diet is interrupted. Third, blueberry supplementation might possibly reverse some degree of memory impairment that has already developed.
"This raises the possibility that this sort of nutritional intervention might still be beneficial even after certain memory deficiencies have become evident," they added.
Nutrition; Published online ahead of print. May 2011