Green Tea Helps Keep Arteries Clear
If you're going to drink green tea in
hopes of preventing heart disease, you should start sipping before
your arteries begin to harden.
A new animal study suggests that
while an important antioxidant in green tea can help prevent the
formation of plaques that can block blood flow, it has no effect
on the fatty deposits once they have formed. Researchers at Cedars-Sinai
Medical Center in Los Angeles report the finding in the May 25
issue of Circulation.
The study used the antioxidant
epigallotcatechin-3-gallate (EGCG), the most powerful of the flavonoids
that have been shown to provide protection against heart disease
The EGCG, provided by Lipton Tea,
was injected into mice that were genetically predisposed to rapid
development of plaque whose arteries had been injured to spur
that development. Other mice of the same strain with similar damage
did not get the antioxidant.
Examination of the arteries after
three and six weeks showed that the formation of new plaque in
mice who got EGCG was reduced significantly, while plaques continued
to form in the mice that did not get the antioxidant. However,
the treatment had no effect on plaque that existed when the injections
"It appears that antioxidant therapy
would have therapeutic benefits only if initiated during a critical
window very early in the formation of plaque," said study author
Dr. Kuang-Yuh Chyu, an assistant professor of medicine at the
University of California, Los Angeles.
Antioxidants are believed to prevent
atherosclerosis by protecting the delicate inner surface of the
blood vessels. But while antioxidants have worked in laboratory
tests and animal studies, results in human trials have been disappointing.
Most animal studies "are started
when the animals are young, while randomized clinical trials typically
enroll adult patients with varying stages of plaques," Chyu noted.
The study is "a small step toward
understanding why the antioxidant story is very complex," said
Dr. Robert A. Vogel, a professor of medicine at the University
of Maryland School of Medicine who has done research in the field.
"We think antioxidants are good,"
Vogel said. "However, when you look at the many human trials that
have been undertaken with antioxidants, the results have been
There is always a difference between
animals kept under carefully controlled conditions and "free-living
human beings doing lots of good and bad things," Vogel said.
As for the timing of antioxidant
use, "until a trial in humans shows that they reduce atherosclerosis,
we don't know if they will be effective early, late or any time,"
There is no harm and some possible
good in drinking green tea, Vogel said, but he advised against
"Data on vitamin supplements to
prevent heart disease is totally lacking," he said.
An explanation of how antioxidants
work is offered by the American
Heart Association. The University of Nebraska Medical Center
has more on the
health benefits of green tea.
Reference Source 101