030422 - Study: Tea Boosts the Body's Defenses 
          
         - Drink Tea to Stay Germ-Free: Report
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Tea - black, green or oolong tea
        - L-theanine – ethylamine – gamma-delta T cell – interferon (key chemical against infection)

Ethylamine – found in some vegetable and wine.
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Study: Tea Boosts the Body's Defenses

By PAUL RECER, AP Science Writer 

WASHINGTON - An ordinary cup of tea may be a powerful infection fighter, a study suggests. Researchers report in the Proceedings of the National Academy of Sciences (news - web sites) that they have found in tea a chemical that boosts the body's defense fivefold against disease. 

They said the chemical primes immune system cells to attack bacteria, viruses and fungi and could, perhaps, be turned into a disease-fighting drug someday. 

Dr. Jack F. Bukowski of Brigham and Women's Hospital in Boston and Harvard Medical School (news - web sites) said Monday that he and his co-authors isolated the chemical in the laboratory and then proved with a group of volunteers that it did protect against germs. 

"We worked out the molecular aspects of this tea component in the test tube and then tested it on a small number of people to see if it actually worked in human beings," said Bukowski. The results, he said, gave clear proof that five cups of tea a day sharpened the body's defenses against disease. 

Penny Kris-Etherton, a nutrition specialist at Pennsylvania State University, 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, involving more people. 

In the study, Bukowski and his co-authors isolated from ordinary black tea a substance called L-theanine. He said the substance is found as well in green and oolong tea, which also are processed from traditional tea tree leaves. 

Bukowski said L-theanine is broken down in the liver to ethylamine, a molecule that primes the response of an immune blood cell 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. 
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Drink Tea to Stay Germ-Free: Report

By Alison McCook 

NEW YORK (Reuters Health) - Drinking tea appears to boost the immune system, perhaps helping people fight off or blunt the effect of infections, researchers said Monday. 

Non-tea drinkers who downed five to six small cups of black tea per day for two weeks appeared to be better able to fight off bacterial infections, according to the report. 

As an explanation for tea's benefits, experiments in the lab revealed that an ingredient found in black, green, oolong and pekoe teas boosted the ability of immune system cells to attack a bacterial invader. 

The experiments used ethylamine, which is produced when the tea ingredient L-theanine is broken down in the liver. 

Previous research suggests that ethylamine, which is also found in vegetables and wine, may target other pathogens as well, including parasites, viruses, and perhaps tumors. 

Based on these findings, people looking to ward off diseases might want to add certain teas to their menu, study author Dr. Jack F. Bukowski of Brigham and Women's Hospital and Harvard Medical School (news - web sites) in Boston, Massachusetts, told Reuters Health. 

"I think the elderly would benefit a lot from drinking tea," he said. "I think there's no downside to it." 

However, he added that regular tea drinkers still get sick, so people should not throw out their medicine cabinet or tell off their doctors just yet. 

"Drinking tea isn't a treatment or a cure for anything," Bukowski cautioned. 
"Probably most (tea drinkers) will still get sick. But people who do get sick will probably get a milder case," he said. 

The study findings appear in the online early edition of the Proceedings of the National Academy of Sciences (news - web sites). 

During the study, Bukowski and his colleagues measured the activity of immune system cells called gamma delta T cells in people who normally did not drink tea. 

Gamma delta T cells are an arm of the immune system charged with preventing and cushioning the blow of diseases. Previous experiments have shown that exposing these cells to ethylamine boosted the abilities of the cells to fight infections. 

During the study, Bukowski and colleagues extracted gamma delta T cells from people and exposed them to ethylamine. After the cells were mixed with bacteria, the researchers saw that those that had not been exposed to ethylamine mounted no attack against the bacteria. However, cells that had been previously exposed to the tea component multiplied by 10-fold, and therefore produced larger amounts of a chemical that fights bacteria. 

And in experiments with people, the researchers found that after drinking about 20 ounces of tea a day for two weeks, people's gamma delta T cells produced a wealth of anti-bacterial chemicals when exposed to bacteria. In contrast, people who drank coffee instead of tea during the study produced no disease-fighting proteins in response to bacteria. 

Despite the supposed power of tea to fight infection, Bukowski urged people to maintain a healthy perspective on the findings. 

"If people are sick, they shouldn't start drinking tea to get better," he said. "They should go to the doctor." 

SOURCE: Proceedings of the National Academy of Sciences 2003;10.1073/pnas.1035603100.