Steeped In Health

By Christine Gorman

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 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 (for the record, it was Lipton) on 11 healthy non--tea drinkers and compared them with 10 healthy people who began drinking coffee. The researchers found that drinking 20 oz. 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, by contrast, 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.

Before you rush out to stock up on tea bags, however, there are a few things you need to know. The evidence of tea's benefits is still contradictory. A few large epidemiological studies support the health claims, but others do not. Smaller experiments, like the Brigham and Women's study, can only hint at theoretical benefits. They don't prove anything. Even if tea does turn out to be some kind of general immune-system booster, the effect can't be that strong. After all, there are millions of tea drinkers in China, and yet diseases like SARS somehow manage to take hold and spread.

Finally, a word about the different types of tea. There is only one true tea plant, Camellia sinensis. (Herbal teas are made from other plants.) The main varieties--black, green and oolong--reflect different processing techniques. If tea is in fact an immune booster, you would expect all three varieties to be equally effective since they are all broken down by the body into molecules that mimic bacterial proteins. There are differences, however, in the types and amounts of disease-preventing antioxidants various teas contain. Green tea has more of the chemically simpler antioxidants called catechins, whereas black tea contains more complex antioxidants called theaflavins and thearubigins. Chemically, oolong tea is a bit of a mix of the other two. Doctors still 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 first and foremost one of life's simple pleasures. If you enjoy it, by all means, 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.