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Articles June 2013 Issue

Green Tea Protects Brain Cells

A flurry of new studies is raising hope that green tea may someday be a potent weapon in the fight against Alzheimer’s disease and other forms of dementia. Although the studies differ widely in technique, ranging from scan-ning people’s brains to forming Alzheimer’s plaques in a test tube, all focus on ways polyphenol compounds in green tea affect important areas of the brain. The studies used extracts of green tea—notably a polyphenol compound called EGCG (epigallocatechin-3-gallate)—but experts say similar benefits could be gained sim-ply by sipping tea.

“As some research has revealed the potential benefit of selected vitamins and fatty acids in promoting cognitive function,” says Jeffrey B. Blumberg, PhD, director of Tufts’ HNRCA Antioxidants Research Laboratory, “recent studies on flavonoids, phytochemicals especially rich in plant foods like berries and tea, show they too may act to promote brain performance and/or reduce the risk for neurodegenerative conditions.”

In one new study, published in the European Journal of Clinical Nutrition, Swiss researchers used functional magnetic resonance imaging (fMRI) to watch the brains of 12 healthy volunteers as they performed tasks testing “working memory.” This type of memory allows the brain to simultaneously store and process information; it’s important to such complex cognitive tasks as language comprehension, learning and reasoning. Participants’ brains were scanned after the subjects had consumed two different doses of a beverage containing green-tea extract, as well as a placebo drink.

Compared to the placebo, the green-tea beverages were associated with increased activity in the dorsolateral prefrontal cortex of the brain. That’s a key area for working-memory processing. Significantly, the activity was greater still with the higher dose of the green-tea extract—what scientists call a dose-response relationship, a sign of cause and effect. Researchers noted that this was the first neuroimaging study to show that fMRI could examine how green-tea extract works on the brain. They said the findings “suggest that green-tea extract may modulate brain activity in the dor-solateral prefrontal cortex.”

PROTECTING PLASTICITY: A second study used mice to test the brain-cell effects of EGCG in green tea. Chinese researchers, publishing their findings in Molecular Nutrition & Food Research, added an EGCG solution to brain cells from white mice.

The cells were taken from the hip-pocampus, a tiny part of the inner brain that acts as a sort of hard drive for memories, indexing them and sending them to other parts of the brain when needed. The production of nerve cells (“neurogenesis”) in the hippocampus of adult brains is important to brain plasticity—the ability of the brain to change in response to new inputs. This neurogen-esis decreases with age, a dropoff that’s also associated with various neurological disorders and cognitive decline.

Researchers found that treatment with EGCG significantly increased the number of cells associated with neuro-genesis. When mice were injected with EGCG, their performance in navigating a maze markedly improved—a sign of increased spatial cognition.

INTERRUPTING ALZHEIMER’S: Two other new studies tested whether green-tea extracts could block the formation of the amyloid plaques associated with Alzheimer’s disease; one of the studies also tested resveratrol, a compound found in red wine.

British scientists, reporting their findings in the Journal of Biological Chemistry, formed “balls” of amyloid proteins in the lab—similar to the toxic, sticky aggregations that attach to nerve cells in the brains of Alzheimer’s patients. Experimenters then added extracts from green tea and red wine to the amyloid balls. Both extracts caused the shape of the balls to distort in such a way that they could no longer bind to nerve cells and disrupt their functioning.

The researchers likened the amyloid balls’ normally precise attachment to nerve cells to “the way a baseball fits snugly into its glove.” After EGCG and resveratrol altered the shape of the balls, the toxic proteins no longer “fit.”

Simon Ridley, MD, head of Alzheim-er’s Research UK, which partly funded the study, commented, “While these early-stage results should not be a signal for people to stock up on green tea and red wine, they could provide an impor-tant new lead in the search for new and effective treatments.”

The positive findings were under-scored, moreover, by similar research at the University of Michigan, published in the Proceedings of the National Academy of Sciences. A multidisciplinary research team of chemists, biochemists and biophysicists investigated the structural effects of EGCG on amyloid plaques. They found that the green-tea compound prevented the formation of potentially dangerous amyloid aggregates. The EGCG extract also actually broke down existing aggregates in proteins that con-tained metals—copper, iron and zinc—associated with Alzheimer’s disease.

Comments (5)

As I've found with many articles dealing with promising research, there is a consistent lack of applicability to end users (your readers). If there is no way that the information can be used in everyday activity, it would seem helpful to state that somewhere in the piece. Conversely, you would be remiss if you did not mention how information could be of use to your readers.

Posted by: K Nazarian | January 27, 2014 8:29 AM    Report this comment

Please provide dosage amounts for the nutritional products used in the studies, e.g., the amounts of EGCG and Resveratrol.

Posted by: Dan Rosenthal | January 27, 2014 11:04 AM    Report this comment

Can we assume that 3 or 6 or ?? cups per day of green tea could make a positive difference for elders or must one have been drinking green tea for years? Or is no researcher willing to state both the amount that might make a difference or the number of years of consuming some specified amount that could make a difference? JoyceL

Posted by: Joyce Leanse | January 27, 2014 12:34 PM    Report this comment

There's no magic amount of green tea associated with benefits, but studies typically have tested tea or tea extract equivalent to about three to six cups daily. If you are a subscriber, you can read more about green tea in our April 2013 Special Report at http://www.nutritionletter.tufts.edu/issues/9_4/special-reports/Drinking-Tea-Protects-Your-Head-Heart-and-Bones_978-1.html.

Posted by: Theresa Jankowski | January 30, 2014 2:08 PM    Report this comment

I am concerned about the amount of caffeine in green tea? or in the extract of green tea? How much is it? Isn't green tea high in caffeine?

Posted by: Maria Davila | June 26, 2014 8:47 PM    Report this comment

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