Drinking tea may help keep the doctor away. A new study finds that tea boosts the body's defenses against infection and contains a substance that might be turned into a drug to protect against disease, US researchers say. Coffee does not have the same effect.

A component in tea was found in laboratory experiments to prime the immune system to attack invading bacteria, viruses and fungi, according to a study in the Proceedings of the US National Academy of Sciences released on Monday. The second experiment, using human volunteers, showed that immune system blood cells from tea drinkers responded five times faster to germs than did the blood cells of coffee drinkers.

"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 Dr Jack, a researcher at Brigham and Women's Hospital in Boston and Harvard Medical School. The results, he said, gave clear proof that five cups of tea a day sharpened the body's disease defenses.