by Craig Weatherby
Early in 2010, research teams from the U.S. and the UK published positive results from the first-ever controlled clinical trials to test the effects of blueberries on brain function in older adults.
In both trials, people who drank blueberry juice or smoothies showed significant improvements in learning and memory, compared with the control groups.
The American researchers also detected a statistical trend towards fewer signs of depression, and lower blood sugar (glucose) levels, among the test group.
These findings have been bolstered by a new study in rats, conducted by scientists from University of Houston and the Tufts University/USDA Human Nutrition Research Center on Aging.
Blueberries reverse mental decline in aging animals
The results of a study in rats showed that eating blueberries for one month slowed and even reversed their age-related decline in mental function (Malin DH et al. 2010).
Rats are ideal for such studies because they age so much more rapidly than humans, allowing researchers to see changes in mere months rather than years or decades.
This study follows one by the same team, which found brain benefits in aging rats fed a blueberry-enriched diet for four months (Goyarzu P et al. 2004).
Elderly rats fed a blueberry-enriched diet for one month showed improvements in memory, as measured in a maze test.
Better yet, eating a blueberry-enriched diet for two months prolonged the benefits after the diet was stopped… and the mental performance of the aging rats improved even more, to the higher level seen in younger rats.
As the researchers wrote, “This illustrates a surprisingly prompt and powerful effect... [of blueberry-enriched diets]” (Malin DH et al. 2010).
They called attention to some promising implications for people:
“First, the present results suggest that even a relatively brief blueberry diet might produce measurable benefits.”
“Second, the benefits of several months of the 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.”
And they raised the question that will occur to many readers: “This raises the possibility that this sort of nutritional intervention might still be beneficial even after certain memory deficiencies have become evident” (Malin DH et al. 2010).
We encourage researchers to test this hope in human clinical trials, sooner rather than later.
How could berries help deter dementia?
Human diets rich in blueberries have previously been linked to a reduced risk of Alzheimer's, and the berries' benefits are believed to flow from their polyphenol content… in particular, two kinds found in most berries, called anthocyanins and flavanols.
We still don't know how anthocyanins and flavanols might enhance memory and other brain functions… but in rats, they're proven to cross the blood-brain barrier and reach areas associated with cognitive performance (Andres-Lacueva C et al. 2005).
As the Houston-Boston team noted, prior studies suggest that berry-borne anthocyanins and flavanols may enhance existing neuronal connections (i.e., links among brain cells), improve cell-to-cell communications, and stimulate growth of brain cells.
We also know that berry-borne polyphenols exert “nutrigenomic” effects on cellular genetic switches called nuclear transcription factors, such as Nf-kappaB (Goyarzu P et al. 2004).
Specifically, they exert damping effects on Nf-kappaB and other pro-inflammatory genetic switches, and may thereby discourage the chronic low-level inflammation associated with Alzheimer's and other degenerative diseases.
Andres-Lacueva C, Shukitt-Hale B, Galli RL, Jauregui O, Lamuela-Raventos RM, Joseph JA. Anthocyanins in aged blueberry-fed rats are found centrally and may enhance memory. Nutr Neurosci. 2005 Apr;8(2):111-20.
Chance R. Food for Thought. British Science Association, September 14, 2009. Accessed at http://www.britishscienceassociation.org/
Derbyshire D. A bowl of blueberries keeps the brain active in the afternoon. The Daily Mail UK, September 14, 2009. Accessed at http://www.dailymail.co.uk/
Goyarzu P, Malin DH, Lau FC, Taglialatela G, Moon WD, Jennings R, Moy E, Moy D, Lippold S, Shukitt-Hale B, Joseph JA. Blueberry supplemented diet: effects on object recognition memory and nuclear factor-kappa B levels in aged rats. Nutr Neurosci. 2004 Apr;7(2):75-83
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Malin DH, Lee DR, Goyarzu P, Chang YH, Ennis LJ, Beckett E, Shukitt-Hale B, Joseph JA. Short-term blueberry-enriched diet prevents and reverses object recognition memory loss in aging rats. Nutrition. 2010 Dec 16. [Epub ahead of print]
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Williams CM, El Mohsen MA, Vauzour D, Rendeiro C, Butler LT, Ellis JA, Whiteman M, Spencer JP. Blueberry-induced changes in spatial working memory correlate with changes in hippocampal CREB phosphorylation and brain-derived neurotrophic factor (BDNF) levels. Free Radic Biol Med. 2008 Aug 1;45(3):295-305. Epub 2008 May 5.