Researchers at Harvard have found that drinking tea may help protect against microbial infections and possibly tumors, thanks to l-theanine, an amino acid found in tea. The researchers studied the blood vessels of non-tea drinkers who had consumed approximately 600 ml daily of black tea for either two or four weeks, and of non-tea, non-coffee drinkers who drank 5-6 cups of instant coffee per day.
In the cells from the tea drinkers, brief exposure to the tea's l-theanine, which is turned into ethylamine in the liver, a "memory response" was triggered when bacteria were introduced. The cells multiplied and produced larger amounts of IFN-g, a bacteria-fighting chemical. Cells that were not exposed to tea did not produce this response.
(Source: Vitamin Retailer, July 2003.)