Contact: Enrique Rivero
University of California - Los Angeles
Green, black tea can reduce stroke risk
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
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.
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."
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.
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."
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
"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.
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.
co-authors with Arab are Weiqing Liu, a senior statistician in the UCLA
Department of Biomathematics, and David Elashoff, associate professor
of medicine in the division of general internal medicine and health
services search at the David Geffen School of Medicine at UCLA.
The Unilever Lipton Institute of Tea funded this study.
General Internal Medicine and Health Services Research Divison in the
department of medicine at the David Geffen School of Medicine at UCLA
provides a unique interactive environment for collaborative efforts
between health services researchers and clinical experts with
experience in evidence-based work. The division's 100-plus clinicians
and researchers are engaged in a wide variety of projects that examine
issues related to access to care, quality of care, health measurement,
physician education, clinical ethics and doctor-patient communication.
Researchers in the division have close working relationships with
economists, statisticians, social scientists and other specialists
throughout UCLA and frequently collaborate with their counterparts at
the RAND Corp. and the Charles Drew University of Medicine and Science.