Powerful antioxidants called flavanols abound only in berries, grapes, cocoa, and some other colorful plant foods.
Their abundance in colorful foods is no coincidence, since some antioxidants from the flavanol family lead double lives as red-blue-purple pigments.
Almost all of the numerous cell and animal studies on this subject suggest that berry-borne flavanols enhance and protect aging brains (Search our newsletter archive)
Today brought us news from two new studies, both testing whether berries could improve brain performance... and the answer, in people aged 18 to 65 and older, was "yes”.
Before we look at the studies, let's review why researchers think that flavanol-rich fruits might enhance people's everyday mental performance... and deter or diminish dementia.
Berry flavanols enhance brain-cell connections and performance
Recent research indicates that rather than acting only as antioxidants, the flavanols in berries, grapes, and cocoa interact directly with neurons (brain cells) at the molecular level.
This interaction may initiate "signaling pathways” that enhance connections among neurons, improve cell-to-cell communications and stimulate regeneration of brain cells.
The enhancement of both short-term and long-term memory is known to be controlled at the molecular level in neurons.
This research suggests that the ability of flavanols to induce improvements in memory may be through the activation of signaling pathways in the hippocampus… a key part of the brain when it comes to learning and memory.
And thanks to earlier USDA-Tufts research, we know that when rats eat berries, flavanols from the fruit show up in parts of their brains associated with thinking, memory, and mood… such as the cerebellum, cortex, hippocampus, and striatum (Andres-Lacueva C et al. 2005).
(Since the blood-brain barriers in rats and humans are highly similar, it's reasonable to presume that berry-borne flavanols reach the brains of human consumers, too.
UK study finds blueberries enhance brain performance across all ages
Dr. Jeremy Spencer of Reading University has led some of the basic research on flavanols' effects in the brain.
Now his team has reported that blueberries enhance brain performance in the real world. Their study was presented at last fall's British Science Festival (Chance R 2009; Derbyshire D 2009).
Dr. Jeremy Spencer's crew recruited 40 volunteers aged 18 to 30, and another set of 40 volunteers aged 65 or older.
Each age set was divided into two groups:
The test group got a mid-morning blueberry smoothie made with 200 grams (seven ounces) of blueberries.
The control group got a mid-morning "control” smoothie containing the same ingredients and calories, but no blueberries.
An hour after the smoothie the test and control groups in each age set carried out 45 minutes of computer-based mental tests of concentration and short term working memory.
The tests were then repeated five hours after the smoothies were consumed.
While no differences were seen during the tests taken right after downing the smoothie, the people in both age sets who drank a blueberry smoothie in the morning were better at concentrating later in the day.
Dr. Spencer said the brain boosting power was not unique to blueberries: "From our studies, other foods containing flavonoids—such as strawberries, cocoa and raspberries—would be similar.”
The Reading researchers believe that—among other effects, such as enhanced cell connections and signaling—the flavanols in berries activate an enzyme in the body called Enos, which increases the flow of blood and oxygen to the brain.
U.S. trial shows memory gains from blueberries
A team led by Dr. Robert Krikorian of the University of Cincinnati conducted the first human trial testing the effects of blueberries on brain function in older adults.
The participants were chosen because they showed early-stage memory problems… a diagnosis linked to increased risk of Alzheimer's or other forms of dementia.
The study was co-authored by scientists from the USDA-Tufts lab and Canada's Agriculture and Agri-Food agency (Krikorian R et al. 2010).
For the blueberry-brain study, they recruited nine older people, whose average age was 76.2.
To serve as a control group, Dr. Krikorian's team asked several people of similar age and medical status to consume an antioxidant-free, blueberry-flavored placebo beverage for 12 weeks.
The participants were all weighed, and each was assigned to drink an amount of blueberry juice (or placebo beverage) equal to about 7.5 milliliters per kilogram of body weight per day (i.e., 1/5 oz. juice per 2.2 lbs. body weight).
For example, a 130-pound person would need to drink two 8 oz. glasses of blueberry juice per day to reach the intake level tested.
The juice used in the study was provided by the Wild Blueberry Association of North America.
The team found that the blueberry juice group showed significant improvements in learning and memory, compared with the control group.
The researchers also detected a statistical trend towards fewer signs of depression, and lower blood sugar (glucose) levels, among the test group.
Dr. Krikorian and his co-workers said they hope to perform research to see whether changes in cognitive function are associated with metabolic improvements… such as the blood-sugar-lowering effects seen in this study.
The scientists expressed cautious hope in their paper: "Interpretation of our findings should be tempered because of the relatively small sample size… [however,] comparison with the analogous placebo beverage data provides some assurance that the observed changes in memory performance were… [attributable to the drink].”
Findings echo 2009 grape trial
The new findings fit with those from a prior human study using grape juice.
Last year, the same research team reported the positive results of a 12-week clinical trial designed to test the effects of Concord grape juice in 12 older adults with memory decline but not dementia.
They observed significant improvements in a measure of verbal learning, and non-significant enhancement of the subjects' verbal and spatial recall.
As they wrote, "These preliminary findings suggest that supplementation with Concord grape juice may enhance cognitive function for older adults with early memory decline…” (Krikorian R et al. 2009).
- 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/ web/ News/FestivalNews/_FoodForThought.htm
- 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/health/article-1212579/ A-bowl-blueberries-day-keeps-brain-active-afternoon.html
- Krikorian R, Nash TA, Shidler MD, Shukitt-Hale B, Joseph JA. Concord grape juice supplementation improves memory function in older adults with mild cognitive impairment. Br J Nutr. 2009 Dec 23:1-5. [Epub ahead of print]
- Krikorian R, Shidler MD, Nash TA, Kalt W, Vinqvist-Tymchuk MR, Shukitt-Hale B, Joseph JA. Blueberry Supplementation Improves Memory in Older Adults (dagger). J Agric Food Chem. 2010 Jan 4. [Epub ahead of print]
- Macready AL, Kennedy OB, Ellis JA, Williams CM, Spencer JP, Butler LT. Flavonoids and cognitive function: a review of human randomized controlled trial studies and recommendations for future studies. Genes Nutr. 2009 Dec;4(4):227-42. Epub 2009 Aug 13.
- Spencer JP. Flavonoids and brain health: multiple effects underpinned by common mechanisms. Genes Nutr. 2009 Dec;4(4):243-50. Epub 2009 Aug 15.
- 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.