A Harvard Medical School study discovered that regular consumption of tea could boost the body’s defenses against infection. 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 National Academy of Sciences.

A 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. Researchers claim that the results give clear proof that five cups of tea a day sharpen the body’s disease defenses.

 In the study a substance called L-theanine was isolated from ordinary black tea. L-theanine is broken down in the liver to ethylamine, a molecule that primes the response of an immune system element called the gamma-delta T cell, considered the first line of defence against bacteria, viral, fungal and parasitic infections.

The T cells prompt the secretion of interferon, a key part of the body’s chemical defense against infection. To further test the finding, the researchers had 11 volunteers drink five cups a day of tea, and 10 others drink coffee. Before the test began, they drew blood samples from all 21 test subjects.

After four weeks, they took more blood from the tea drinkers and then exposed that blood to the bacteria called E-coli. The immune cells in the specimens secreted five times more interferon than did blood cells from the same subjects before the weeks of tea drinking researchers claimed. Blood tests and bacteria challenges showed there was no change in the interferon levels of the coffee drinkers.