Green tea: Background

Historical Note

Tea has been a popular beverage for thousands of years and was originally grown in China, dating back 5000 years, where it has been used as part of various ceremonies and to maintain alertness. Green tea and the partially fermented oolong tea have remained popular beverages in Asia since that time, whereas blacktea is the preferred beverage in many English-speaking countries. Tea was introduced to the Western culture in the 6th century by Turkish traders. Second to water, tea is now considered to be the world’s most popular beverage.

Common Name

Green tea

Other Names

Chinese tea, camellia tea, grunertea, Matsu-cha

Botanical Name / Family

Camellia sinensis (family Theaceae)

Plant Part Used


Chemical Components

The composition of green tea varies according to the growing and harvesting methods, but the most abundant components are polyphenols, which are predominantly flavonoids (e.g. catechin, epicatechin, epicatechin gallate, epigallocatechin gallate, proanthocyanidins). Caffeine content in green tea varies but is estimated at about 3%, along with very small amounts of the other common methylxanthines, theobromineand theophylline. It also contains many other constituents, such as tannin, diphenylamine, oxalic acid, trace elements and vitamins.

Epigallocatechin gallate is one of the most abundant polyphenols in tea and is regarded as the most significant pharmacologically active component.

Clinical note — The difference between teas

Black, green and oolong tea are produced from the same plant (Camellia sinensis) but differ in polyphenol content according to the way the leaves are processed. Blacktea is made from oxidised leaves whereas oolong tea is made from partially oxidised leaves and green tea leaves are not oxidised at all. Because the oxidising process converts many polyphenolic compounds into others with less activity, green tea is considered to have the strongest therapeutic effects and the highest polyphenol content. Caffeine concentrations also vary between the different teas: black tea > oolong tea > green tea > fresh tea leaf. Variation in caffeine content is further influenced by growing conditions, manufacturing processes and size of the tea leaves. The highest quality leaves are the first spring leaf buds, called the ‘first flush’. The next set of leaf buds produced is called the ‘second flush’ and considered to be of poorer quality. Tea varieties also reflect the area they are grown in (e.g. Darjeeling in India), the form produced (e.g. pekoe is cut, gunpowder is rolled) and processing method (black, oolong or green).