GREEN TEA

Health Benefits of Green Tea

Green tea's popularity in the United States continues to grow. Scientific information that suggests it is a rich, natural source of antioxidants. Most of the green tea research to date has focused on cancer prevention. During the 1980s populations studies found lower rates of cancer in Asian populations who regularly consume green tea. Since then, scientists have been trying to find out why green tea drinkers are less likely to develop cancer, what specific green tea components act to prevent cancer, and exactly how green tea works in the human body. Scientifically important findings suggest that green tea may prevent the following types of cancer in humans: bladder, colon, esophageal, pancreas, rectum, and stomach.


Information from both animal and human studies suggests;

antioxidants in green tea may lower cholesterol; reduce the risk of dying from heart disease, and control blood pressure.

In a 25-year study, tea drinkers consuming more than 8.5 oz. of tea each day had much less risk of dying and a lower rate of first heart attacks than those who drank less tea. Men in the study whose antioxidant intake was greatest had one-third the risk of death from coronary heart disease. In another test tube study, scientists report that antioxidants decrease blood cell clumping, which reduces blood clotting and other risks that commonly happen before heart attacks and strokes. Although these data are ground breaking, more studies with humans are needed to establish the heart benefits from drinking green tea. Scientists suggest green tea helps the liver in two ways - by protecting liver cells and by triggering the immune system. Green tea antioxidants have been shown to protect the liver against toxins like alcohol and chemicals in cigarette smoke. Although the scientific information about the effects of green tea on the liver is limited, the early results look promising and should be studied in greater detail in the future.

Active constituents:

Green tea contains volatile oils, vitamins, and minerals, (no caffeine), but the active constituents are polyphenols, particularly the catechin called epigallocatechin gallate (EGCG). The polyphenols are believed to be responsible for most of green tea's roles in promoting good health.

Green tea is manufactured from fresh, unfermented tea leaves; the oxidation of catechins is minimal, and hence they are able to serve as antioxidants. Researchers believe that catechin is effective because it easily sticks to proteins, blocking bacteria from adhering to cell walls and disrupting their ability to destroy them. Viruses have ‘hooks’ on their surfaces and can attach to cell walls. The catechin in green tea prevents viruses from adhering and causing harm. Catechin reacts with toxins created by harmful bacteria (many of which belong to the protein family) and harmful metals such as lead, mercury, chrome, and cadmium.

Tannin in green tea is mostly catechin and is a key component in its taste providing the astringency. The amount of catechin tends to increase as the season progresses. Spring tea (first crop) contains 12-13% catechin (13-17% as tannin) while summer tea (third crop) contains 13-14% (17-21% as tannin). If leaf order is compared, younger leaves include more catechin than mature ones. First leaves contain 14%, second 13%, third 12%, and fourth 12%. This explains why second and third crop summer teas are more astringent while Bancha is less so. Gyokuro green tea, whose leaves are covered during growth, contains less catechin and astringency (10% as tannin) because it gets less sunshine then Sencha.

Update: 4-9-2009

Thanks to a site user tip we now have a study that indicates green tea may also help contol blood glucose.

 There is a study published in The journal of Biologic Chemistry:

Green Tea Polyphenols Modulate Insulin Secretion by Inhibiting Glutamate Dehydrogenase^*http://www.jbc.org/cgi/reprint/M512792200v1

From the Donald Danforth Plant Science Center, St. Louis, Missouri 63132, Endocrinology Division, Abramson Research Center, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, and ^¶Diabetes Research Center and Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104