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Green Tea

Posting Date: 08/26/2002

Green tea, like black tea, is rich in tannins. Tannic acids make up 9 to 20 percent of the leaves.

Flavonoids including apigenin, kaempferol, myricetin, and quercetin have also been identified, but at low concentrations. Some flavonoids unique to black tea are theaflavins, theasinensins, thearubigens, and theacitrins.

Another set of flavonoids has been intensively studied recently. These polyphenols (catechins) are not vitamins, but they seem to have strong antioxidant properties.

Epigallocatechin-3-gallate (EGCG) in particular has been identified as capable of protecting experimental animals from radiation damage and possibly reducing the risk of cancer.

Green tea is especially rich in EGCG. With fermentation, many of the polyphenols are oxidized. This alters the composition of black tea in comparison to green tea (which is very similar in composition to the fresh leaves).

Tea appears to concentrate certain minerals in its leaves. Both fluoride and aluminum can be detected.

Uses

Current interest in green tea in the United States has focused mainly on its cancer preventive properties rather than on its flavor, which may be an acquired taste.

Japanese researchers were the first to report that people living in an area where green tea was an important crop were only half or even a fifth as likely to develop cancer as those in an area that did not grow tea.

There seems to be an inverse relationship between drinking tea and developing cancer of the digestive tract or urinary system. One recent epidemiological study in Japan showed that men who drank ten or more cups of green tea daily had a significantly lower risk of lung, liver, colon, or stomach cancer.

EGCG seems to be responsible in large measure for inhibiting the growth of cancer cells and mopping up free radicals that can damage healthy cells.