for National Geographic News
Next to water, tea may be the most commonly consumed drink on the planet. The British alone consume around 165 million cups of Earl Grey, Assam, Darjeeling, Oolong and numerous other varieties of tea each day. Now, new research adds to increasing evidence that tea is not only a much-loved beverage, but may offer a host of health benefits as well.
A new study, published online in the journal Proceedings of the National Academy of Sciences, reveals how substances found in tea may help prime the body's immune system to fight off infection. Another report shows how substances in green tea may be linked to skin-cell rejuvenation.
The findings "add to the enormous body of evidence that tea can make a contribution to a healthy lifestyle," commented Bill Gorman executive director of The Tea Council, an independent tea-promotion body based in London, England.
Other studies have shown that antioxidant chemicals in teaproduced from the aromatic plant Camellia sinensiscan help minimize the risk of developing stomach and other types of cancer. One study showed that drinking one cup of tea a day could also reduce heart attack risk by up to 50 percent.
Brewing Up a Defense Force
This latest study shows how chemicalsknown as alkylamineswhich are commonly present in tea (as well as wine, apples, mushrooms, and other sources), are also present in some bacteria, cancerous cells, parasites, fungi, and other disease-causing agents.
Drinking tea may be able to prime the body's immune system against these agents, by teaching disease-fighter immune cells to recognize and remember alkylamines.
"We found that alkylamines made by bacteria were recognized by the immune system, and wondered where else in nature they occurred," said study co-author Jack F. Bukowski, immunologist at Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts. A quick scan of the literature confirmed that the chemicals were commonly present in tea.
Bukowski and his colleagues carried out experiments which revealed that exposing blood to these chemicals in the test tube could increase the size of one type of defensive response to simulated infection by up to five times. In contrast, human blood cells not exposed to alkylamines showed a much less significant response to simulated bacterial infection.
Tea 1; Coffee 0
In a further experiment, Bukowski showed that the same kind of increased response to infection also occurred in the blood of regular tea drinkers, but not that of coffee drinkers.
To investigate the response in humans, the researchers recruited 21 non-tea-drinker volunteers to drink either five to six small cups of black tea or five to six small cups of instant black coffee daily for four weeks. Tea contains alkylamine mostly in the form of its precursor chemical L-theanine. Coffee doesn't contain the chemical.
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