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Green Tea (Camellia sinensis)
Green tea consist of the leaves and delicate young leaf buds of an evergreen bush (Camellia sinensis) widely cultivated in Asia. Green tea is the freshest and least processed form of tea, the most popular human-made beverage in the world.

Traditional Uses:
Traditionally used by monks as a mild mental stimulant, green tea also has a long history as a medicinal herb, useful for treating coughs, colds, and breathing ailments.

Modern Uses:
In recent years scientists have begun to verify green tea's remarkable health-promoting properties. Studies indicate that green tea may help protect against cancers of the lungs, skin, liver, pancreas, and stomach. Green tea benefits the heart by lowering cholesterol levels and reducing the tendency of blood platelets to stick together. It appears to reduce the incidence of dental caries and has shown promise as a weight-loss agent that can promote the burning of fat and help to regulate blood sugar and insulin levels.
Green tea contains potent antioxidants called catechins, and tea extract is proven to increase antioxidant activity in the blood. In one study, human volunteers were supplemented with single doses of green tea catechins in free or in a phospholipid complex (phytosome) form, each containing 400 mg of epigallocatechingallate (EGCg)-a particularly potent antioxidant polyphenol. EGCg was chosen as bio-marker for green tea catechin absorption, and blood levels over time were correlated to the subsequent percent variations of blood ascorbate, total glutathione, alpha-tocopherol, beta-carotene and total-antioxidant levels (Total Radical Antioxidant Parameter or TRAP). Green tea catechins were absorbed better when administered as phospholipid complex (phytosome) rather than as free catechins. Single dose intake of both forms of catechins produced a transient drop (10-20%) in blood ascorbate and total glutathione levels, but it increased total antioxidant levels (TRAP) by 16-19%. These variations were consistent with the blood levels of EGCg, ascorbate and total glutathione.

Recent findings:
• Japanese researchers reported that increased consumption of green tea prior to clinical cancer onset is significantly associated with improved prognosis of stage I and II breast cancer. Green tea appears to inhibit various human tumors in test tubes, including specific leukemic and skin cancers, plus carcinomas of the breast, gastrointestinal tract, colon, and lung.
• Topical application of the major polyphenol antioxidant in green tea (EGCg) reduces the amount of free radicals and inflammatory prostaglandins produced by immune cells in skin in response to UVB sun rays. The results suggest that skin products containing sufficient green tea extract may help protect against UVB-induced skin aging and skin cancers.
• Drinking green tea was tested in cancerous mice receiving the chemotherapeutic drug doxorubicin, with positive results suggesting that green tea may enhance cancer chemotherapy and patients' quality of life.

Do Scientists Know How It Works?
Green tea has been found to contain numerous polyphenol compounds, such as the flavonoid catechin, with antioxidant and health-promoting properties. It has more of these beneficial compounds than fermented black tea.

Types of products:
The most popular green tea products are the dried herb for making tea, available in various grades (from twiggy kukicha to choice sencha) and forms (loose, tea bags), and encapsulated extracts standardized for 25 percent or higher of the polyphenols. Green tea has also become a popular ingredient in sun blocks, cream rinses, and other body care products.

Safety:
The most worrisome chemical in green tea is caffeine, which occurs in small amounts (20 to 30 mg per cup, if brewed for 2 to 3 minutes) compared to coffee. Unless caffeine is added, caffeine content of the capsules should be approximately 5 to 15 mg. The potential health benefits from consuming four to five cups of green tea per day apparently outweigh any negative effects of caffeine. An increased risk of cancer of the esophagus has been associated with some tea-drinking populations, but the effect is apparently from drinking large amounts of extremely hot, salty tea.
The evidence for green tea's potent antioxidant effects continues to accumulate. In a recent study, researchers found that compounds such as those found in tea not only directly scavenge free radicals but also enhance the effectiveness of the body's natural antioxidant systems.

References

• Anon., "Proceedings and abstracts presented at the First International Symposium on the Physiological and Pharmacological Effects of Camellia sinensis (Tea)," Preventative Medicine (1992), 21:329-553
• Dulloo, A.G., et al., "Tealine and thermogenesis: Interaction between polyphenols, caffeine and sympathetic activity," International Journal of Obesity (1996), 20(S4):71
• Gutman, R.L., and B.-H. Ryu, "Rediscovering tea: An exploration of the scientific literature," HerbalGram (1996), 37:33-48
• Hertog, M.G.L., et al., "Dietary antioxidant flavonoids and risk of coronary heart disease: The Zutphen Elderly Study," The Lancet (1993), 342:1007-11
• Imai, K., and K. Nakachi, "Cross-sectional study of effects of drinking green tea on cardiovascular and liver diseases," British Medical Journal (1995), 310:693-96
• Katiyar, S.K., and H. Mukhtar, "Tea in chemoprevention of cancer: Epidemiologic and experimental studies," International Journal of Oncology (1996), 8:221-38.
• Katiyar SK, et al. Polyphenolic antioxidant (-)-epigallocatechin-3-gallate from green tea reduces UVB-induced inflammatory responses and infiltration of leukocytes in human skin. Photochem Photobiol. 1999 Feb;69(2):148-53. Review.
• Kuroda Y, et al. Antimutagenic and anticarcinogenic activity of tea polyphenols. Mutat Res. 1999 Jan;436(1):69-97. Review.
• Nakachi K, et al. Influence of drinking green tea on breast cancer malignancy among Japanese patients. Jpn J Cancer Res. 1998 Mar;89(3):254-61.
• Otake S, et al. Anticaries effects of polyphenolic compounds from Japanese green tea. Caries Res. 1991;25(6):438-43.
• Otsuka T, et al. Growth inhibition of leukemic cells by (-)-epigallocatechin gallate, the main constituent of green tea. Life Sci. 1998;63(16):1397-403.
• Pietta P, et al. Relationship between rate and extent of catechin absorption and plasma antioxidant status. Biochem Mol Biol Int. 1998 Dec;46(5):895-903.
• Pozniak, P.C., "The carcinogenicity of caffeine and coffee: A review," Journal of the American Dietetic Association (1985), 85:1127-33
• Serafini, M., et al., "In vivo antioxidant effect of green and black tea in man,"
• European Journal of Clinical Nutrition (1996), 50:28-32
• Stoner, G., et al., "Polyphenols as cancer chemopreventive agents," Journal of Cellular Biochemistry 1995, 58(22)169-80.
• Suganuma M, et al. Synergistic effects of (--)-epigallocatechin gallate with (-)-epicatechin, sulindac, or tamoxifen on cancer-preventive activity in the human lung cancer cell line PC-9. Cancer Res. 1999 Jan 1;59(1):44-7.
• Valcic S, et al. Inhibitory effect of six green tea catechins and caffeine on the growth of four selected human tumor cell lines. Anticancer Drugs. 1996 Jun;7(4):461-8.
• You M, et al. Preclinical and clinical models of lung cancer chemoprevention. Hematol Oncol Clin North Am. 1998 Oct;12(5):1037-53. Review.

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