Originating from the Camellia Senesis plant, a warm-weather evergreen, tea has been consumed by all cultures for over 4,000 years. Tea is grown in the tea gardens and estates of over 30 different countries, resulting in thousands of flavorful variations. The world consumes over 3 billion kilos of tea each year. Like wines, each tea takes its name from the district in which it's grown, and each district is known for producing tea with unique flavor and character. Tea is also divided by grades, determined by leaf size.

How the fresh leaves of the tea plant are processed and their level of contact with oxygen determine resulting types of tea. During oxidation, tea leaves undergo natural chemical reactions that result in distinctive color and taste characteristics. Green tea is not oxidized at all-the leaves are steamed, rolled and dried while black tea is allowed to oxidize for two to four hours. Oolong tea falls somewhere between green and black teas, in that the leaves are only partially oxidized.

In Asia, particularly in China, the positive health effects of tea have been known since ancient times, but it was in the West that effects of specific ingredients in tea were brought to light for the first time. In Japan, studies on the ingredients in tea began in the 1920s. As interest in their effects on health increased, extensive studies of tea began in the 1980s and are ongoing.