Steeped In Health

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Sit down, put on a pot and chalk up another entry in the list of ways that tea drinking may be good for you. Researchers at the Brigham and Women's Hospital in Boston — a Harvard Medical School teaching hospital — have found new evidence that ordinary tea may prime the immune system to fend off attacks from bacteria and other pathogens. "This is the first report of tea affecting the immune system," says Dr. Jack Bukowski, a rheumatologist and co-author of the study. But it's hardly the first health benefit attributed to tea. Over the years, credible claims have been made that tea may help protect against various forms of cancer, cardiovascular disease, Alzheimer's, Parkinson's disease and rheumatoid arthritis.

The Brigham and Women's study looked at the effects of black tea on 11 healthy nontea drinkers and compared them with 10 healthy people who began drinking coffee. The researchers found that drinking 600 ml of tea every day for at least two weeks doubled or tripled the immune system's output of an infection-fighting substance called interferon gamma. The coffee drinkers registered no difference in interferon-gamma production. Apparently the body metabolizes the tea into molecules that mimic the surface proteins of bacteria, jump-starting the immune system so that when real bugs show up, they can more easily be dispatched.

But keep in mind that although a few large epidemiological studies support these claims, others do not. Smaller experiments, like the Brigham and Women's study, only hint at theoretical benefits. Even if tea does turn out to be some kind of general immune-system booster, the effect can't be that strong: there are millions of tea drinkers in China , and yet diseases like sars manage to take hold and spread.

Finally, a word about the different types of tea. Green tea has more of the chemically simpler antioxidants called catechins, whereas black tea contains more complex antioxidants called theaflavins and thearubigins. Oolong tea is a bit of a mix of the other two. Doctors don't know whether one type of tea is better for some conditions than others. It's possible that they all take the body to the same place but by different routes.

As always, use a little common sense. Tea is one of life's simple pleasures. If you enjoy it, go ahead and drink it. But don't expect it to make up for bad habits, like smoking, or for bad luck, like whatever genetic shortcomings you were born with.