Green tea extract is derived from leaves of camellia sinensis, the plant from which green, black and oolong teas are made. Green tea extract is associated with several health benefits, many supported by preliminary scientific research. These benefits include potential cancer-fighting properties, and a strong antioxidant effect that protects the body from the damaging effect of free radicals. The scientific community notes, however, that continued research is necessary.
Green tea has been used for medicinal purposes in India and China for nearly 5,000 years. It is made by lightly steaming leaves of the plant before allowing them to dry. This process retains active properties of the plant. Oolong tea is made by allowing the leaves to ferment slightly before drying, and black tea is made by allowing the leaves to ferment longer. Fermentation breaks down the active ingredients, making green tea or green tea extract the tea of choice.
Green tea extract, like many herbs, is standardized in the production phase to guarantee that a certain percentage of the active ingredients remain present in the final capsulized form. The active ingredients in green tea extract are polyphenols in the form of flavinoids like catechins and epigallocatechin gallate (EGCG). Polyphenols, flavinoids, catechins and EGCG are powerful antioxidants that appear to interfere with and reduce the spread of certain types of cancer cells. The antioxidant activity of EGCG in green tea extract is purportedly up to 100 times more powerful than that of vitamin C or E.
Among populations in China and Japan where high amounts of green tea are consumed daily, cancer rates are statistically lower. There is now growing scientific research from reputable sources that show promising results as to how the active ingredients in green tea extract might be responsible for lowering rates of various kinds of cancer.
UCLA's Jonsson Comprehensive Cancer Center, an award-winning cancer research center, reported in their 2005 Cancer Discoveries newsletter that several published, peer-reviewed studies indicated that green tea extract â€śinduces death in cancer cellsâ€ť without affecting healthy cells, and prevents cancer cells from producing the â€śindependent blood supplyâ€ť required to spread to other parts of the body. This indicates that green tea extract might help to keep cancer contained, making it easier to treat.
Studies conducted by other respected universities and clinics have also showed promising results involving breast, liver, lung and colon cancer, among others. The Mayo Clinic conducted a small study using four patients with chronic lymphocytic leukemia (CLL). Three of the four patients showed significant regression of CLL after taking green tea extract for a period of a few months. The fourth patientâ€™s prognosis was improved, but not significantly. A larger trial is needed to see if these results can be repeated with consistency.
Green tea extract might also be beneficial in improving cardiovascular circulation by reducing LDL or â€śbad cholesterol,â€ť suppressing appetite and improving oxidation of fat. However, these claims are not widely accepted by the scientific community because they are based on animal models, and only a few human studies.
When purchasing green tea extract, look for a product that is standardized to a minimum of 90% polyphenols and 55% EGCG. Using this standard, a 500-milligram (mg) capsule will contain 275mg EGCG, (500mg x 55% = 275mg). The suggested daily dose according to some sources is approximately two cups of green tea per day, or the equivalent of 200-400mg EGCG per day. Note that green tea contains natural caffeine. Processes that remove the caffeine may also diminish the potency of active ingredients. The quality of green tea extract will vary between brands, so read labels carefully and do not exceed the recommended dosage. Green tea extract should not be used in lieu of professional care, and is not recommended for pregnant or lactating women. See your doctor regularly and follow a healthy routine of diet and exercise for optimum health.