WASHINGTON -A wee cuppa tea may help keep the doctor away.
A new study finds that tea boosts the body's defenses against infection and
contains a substance that might be turned into a drug to protect against disease,
researchers say. Coffee does not have the same effect, they say.
A component in tea was found in laboratory experiments to prime the immune s
ystem to attack invading bacteria, viruses and fungi, according to a study in
the Proceedings of the National Academy of Sciences released Monday.
A second experiment, using human volunteers, showed that immune system blood
cells from tea drinkers responded five times faster to germs than did the blood
lls of coffee drinkers.
"We worked out the molecular aspects of this tea component in the test tube
nd then tested it on a small number of people to see if it actually worked in
human beings," said Dr. Jack F. Bukowski, a researcher at Brigham and Women's
Hospital in Boston and Harvard Medical School. The results, he said, gave clear
proof that five cups of tea a day sharpened the body's disease defenses.
Penny Kris-Etherton, a nutrition specialist at Penn State University, a
nutrition expert, said Bukowski's study adds to a growing body of evidence that
tea is an effective disease fighter.
"This is potentially a very significant finding," she said. "We're seeing
multiple benefits from tea."
But she said the work needs to be confirmed in a much larger study,
nvolving more people.
In the study, Bukowski and his co-authors isolated from ordinary black tea a
substance called L-theanine.
Bukowski said L-theanine is broken down in the liver to ethylamine, a
molecule that primes the response of an immune system element called the
gamma-delta T cell.
"We know from other studies that these gamma-delta T cells in the blood are
the first line of defense against many types of bacteria, viral, fungal and
parasitic infections," he said. "They even have some anti-tumor activity."
The T cells prompt the secretion of interferon, a key part of the body's
chemical defense against infection, Bukowski said.
"We know from mouse studies that if you boost this part of the immune
system it can protect against infection," he said.
To further test the finding, the researchers had 11 volunteers drink five
cups a day of tea, and 10 others drink coffee. Before the test began, they
drew blood samples from all 21 test subjects.
After four weeks, they took more blood from the tea drinkers and then
exposed that blood to the bacteria called E-coli. Bukowski said the immune
cells in the specimens secreted five times more interferon than did blood
cells from the same subjects before the weeks of tea drinking. Blood tests and
bacteria challenges showed there was no change in the interferon levels of the
coffee drinkers, he said.
Bukowski said it may be possible to further isolate and refine L-theanine
from tea and use that as a drug to boost the infection defense of the body.
The health effects of tea have been extensively studied. It has been
linked to lower heart disease and cancer risk through the action of flavonoids,
a type of antioxidant. Other studies have linked tea to helping combat
osteoporosis, the brittle bone disease, and to relieving some allergy symptoms.
Abstract of original paper (www.pnas.org)
