GREEN TEA

Green tea has been considered a medicinal remedy in Chinese tradition dating back over 4,000 years. The observed health benefits of this folk remedy now being validated by modern scientific investigation include: lowers total cholesterol, increases HDL cholesterol levels, reduces blood pressure, acts as a "blood thinner" by inhibiting platelet aggregation, reduces risk of heart attack and stroke, reduces risk of cancer, enhances immune cell function, improves digestion, and prevents dental cavities and gingivitis.

Green tea catechins are definitely included in a broad brush approach to the health benefits of flavonoids, which includes potential for the prevention and treatment of cardiovascular disease, cancer, inflammatory conditions, asthma, periodontal disease, liver disease, cataracts, and macular degeneration. Epidemiological studies suggest that populations drinking 8-10 cups of Green tea daily have markedly reduced rates of gastrointestinal cancers as well as lower rates of cancer of the pancreas, breast, and lung. Japan, for example, has a very low incidence of cancer which is thought secondary to their relatively high intake of Green tea.

Laboratory studies supporting the cancer protective effect of Green tea demonstrate that catechins and other polyphenols inhibit free radical precursors to cancer as well as block the effects of other tumor promoters including estrogen, growth factors, and cancer causing chemicals like benzopyrenes and nitrosamines.

The anticancer effect of Green tea polyphenols, specifically catechins, in human and animal studies has been impressive enough for the National Cancer Institute to include Green tea polyphenols in its "Designer Nutrient Program", a research effort to investigate the cancer preventative and therapeutic benefits of foods and food products.

Extensive international research reveals that Green tea catechins have apoptic activity in human cancer cell lines including prostate, skin, lymphoma, ovarian, colon, adenocarcinoma, liver breast, lung, and stomach cancers.

Green tea consumption is protective for gastrointestinal cancers in large studies. Green tea polyphenols have shown promise in vitro as antineoplastic substances, due to their ability to scavenge oxidative initiators of neoplasia (Yoshikawa, Picard).

Laboratory and epidemiological studies indicate Green tea catechins exert a protective effect against prostate cancer. Green tea drinkers have lower rates of prostate cancer with the lowest rate of prostate cancer in China with the highest consumption of tea (Gupta).

Antimutagenic properties of catechins against tumors found in laboratory animals were reproduced recently when tested against four human tumor cell lines from carcinomas of the breast, colon, lung and melanoma. Epigallocatechin gallate was the most potent catechin against all four tumor lines. It was recommended that in vivo animal trials be conducted prior to consideration of testing Green tea catechins against cancer in humans.

Green tea inhibits cancer in laboratory studies by several mechanisms including enhanced cell-mediated immunity, increased glutathione-S-transferase activity (increases glutathione, a powerful intracellular antioxidant), inhibits tumor growth rate, blocks tumor-induced inhibition of intracellular communication, and scavenges free radicals. Green tea polyphenols specifically block the formation of carcinogenic nitrosamines.

Daily intake of Green tea polyphenols appears to have multiple health benefits summarized below, including reduced risk of cancer and cardiovascular disease:

• Catechins have antimutagenic activity against both spontaneous and chemically-induced mutations.
• Catechins have anti-tumor activity, inducing phase I and II metabolic enzymes that increase the formation and excretion of detoxified metabolites of carcinogens, slowing the rate of cell replication and thus the growth and development of neoplasms, and preventing spontaneous and chemically-induced cancer development.
• Catechins have regulatory effects on blood pressure and high blood-pressure induced strokes. Individuals consuming more than five cups a day having a 500% decrease in stroke incidence.
• Catechins have an antihyperglycemic action, lowering both blood-glucose and normalizing insulin release.
• Catechins show antiviral effects, inhibiting reproduction of numerous viruses including influenza and human immunodeficiency virus.
  

Green tea also reduces oxidative stress caused by smoking, including decreased oxidative DNA damage, reduced lipid peroxidation, and reduced urine levels of free radicals. Green tea appears to significantly lower risk of cardiovascular disease, even having a protective effect in smokers. Japanese males, for example, have a relatively low risk of heart disease despite the fact 75% of adults smoke tobacco.