Green, Black Tea Said to Boost Immune System
AFP
health.discovery.com
April 21, 2003 — Certain types of tea have long been known to protect against cancer, but now US researchers have reason to believe they may also boost the immune system.
The findings are very preliminary, but Brigham and Women's researchers reported that volunteers who were asked to drink 20 ounces of black tea a day demonstrated stronger immune responses to infection than they had previously, or than a control group of coffee drinkers.
"The health benefits of tea have been touted for centuries but no human research has demonstrated an association between tea drinking and immunology," said lead author Jack Bukowski.
"Now we have a new explanation for the medicinal effect of tea. Our data suggest that the amino acid L-theanine may specifically boost the capacity of gamma delta T cells — the body's first line of defense against infection."
The researchers had previously shown that L-theanine — commonly found in black, green, oolong and pekoe teas — stimulated certain of the body's white or killer T-cells in laboratory tests.
They speculated that the same effect could be duplicated by drinking tea. And indeed when the researchers took blood samples from 11 volunteers on the tea diet and compared it with the coffee drinkers, they found the tea drinkers produced five times the amount of anti-bacterial proteins — an indication of a stronger immune response.
"Our research suggests that when tea drinkers become exposed to germs, some, but not all, may be protected from getting sick," explained Bukowski, an assistant professor of Medicine at Harvard Medical School.
"And, importantly, those who do become ill, may develop a milder infection or disease compared to non tea drinkers, although further research will be needed to confirm these predicted outcomes."
The study appears in Monday's issue of the Proceedings of the National Academy of Sciences.
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