Tea Boosts Immunity and Helps Skin, Study Finds

John Pickrell in England
for National Geographic News
April 29, 2003
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 tea—produced from the aromatic plant Camellia sinensis—can 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 chemicals—known as alkylamines—which 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.

"As in the test tube, blood taken [from the volunteers] after tea drinking made five times as much of a crucial anti-bacterial substance, compared to before tea drinking," said Bukowski. "Coffee drinking had no such effect."

Alkylamines found in tea are relatively weak, and don't fully activate the immune system's so-called T cells—a vital line of defense—but they do keep them in a state of readiness, said Bukowski. Then, "when bacteria arrive, they bring with them the same antigens, but also other signals that alert the immune system that this is the real thing," he said. This is when an all-out defensive attack takes place.

Studies suggest that "coffee doesn't seem to have any health benefits, but aside from excess caffeine intake, doesn't seem to be detrimental [either]," said Bukowski.

The new findings suggest that drinking tea can promote an increased immune response to bacteria, agreed Stephen Hsu, an expert on tea-related health issues and cell biologist at the Medical College of Georgia, Augusta. "Though there is some evidence that green tea drinking can [influence the immune system by reducing] allergic responses and asthma," this is the best evidence so far that tea can affect the immune system, said Hsu.

However, said Hsu, though the findings are interesting, a "more in-depth study" is required, with a larger group of tea-drinkers to confirm the link.

Refreshing in More Ways than One

Hsu has this week published his own study, in the Journal of Pharmacology and Experimental Therapeutics, revealing that other chemicals found in tea are able to reactivate dying skin cells. "If we can energize dying skin cells, we can probably improve the skin condition," he said.

The finding could one day possibly be applied not only to anti-aging remedies but also to wound healing and the treatment of skin conditions, said Hsu. Some anti-aging cosmetics already contain tea extracts, he said, though their effectiveness has not been scientifically proven.

"When the Chinese reputedly discovered tea, several thousand years ago, they felt that it did them a power of good," said Gorman. Unlike the early proponents of tobacco's healthful benefits, the ancient Chinese may be proved right by modern medical science.

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