Green, black tea can
reduce stroke risk
Monday, February 23,
2009
Drinking at least three cups of green or black tea a day can
significantly reduce the risk of stroke, a new UCLA study has
found. And the more you drink, the better your odds of staving off
a stroke.
The study results, published in the online edition of Stroke:
Journal of the American Heart Association, were presented Feb. 19
at the American Heart Association's annual International Stroke
Conference in San Diego, Calif.
The UCLA researchers conducted an evidence-based review of all
human observational studies on stroke and tea consumption found in
the PubMed and Web of Science archives. They found nine studies
describing 4,378 strokes among nearly 195,000 individuals,
according to lead author Lenore Arab, a professor of medicine in
the division of general internal medicine and health services
research at the David Geffen School of Medicine at UCLA.
"What we saw was that there was a consistency of effect of
appreciable magnitude," said Arab, who is also a professor of
biological chemistry. "By drinking three cups of tea a day, the
risk of a stroke was reduced by 21 percent. It didn't matter if it
was green or black tea."
And extrapolating from the data, the effect appears to be linear,
Arab said. For instance, if one drinks three cups a day, the risk
falls by 21 percent; follow that with another three cups and the
risk drops another 21 percent.
This effect was found in tea made from the plant Camellia sinensis,
not from herbal teas.
There are very few known ways to reduce the risk of stroke, Arab
said. And developing medications for stroke victims is particularly
challenging, given that the drug has to get to the stroke-damaged
site quickly because damage occurs so fast. Arab said that by the
time a stroke victim gets medical care, it's nearly too late to
impede the damage.
"That's why these findings are so exciting," she said. "If we can
find a way to prevent the stroke, or prevent the damage, that is
simple and not toxic, that would be a great advance."
Though no one is certain which compounds in tea are responsible for
this effect, researchers have speculated that the antioxidant
epigallocatechin gallate (EGCG) or the amino acid theanine may be
what helps. Antioxidants are believed to help prevent coronary
artery disease.
"And we do know that theanine is nearly 100-percent absorbed," Arab
said. "It gets across the blood-brain barrier and it looks a lot
like a molecule that's very similar to glutamate, and glutamate
release is associated with stroke.
"It could be that theanine and glutamate compete for the glutamate
receptor in the brain," she added.
Although a randomized clinical trial is needed to confirm this
effect, the findings suggest that drinking three cups of green or
black tea a day could help prevent an ischemic stroke.
###
University of California - Los Angeles
Thanks to University of California
- Los Angeles for this article.
