Monday, June 11, 2007
Green Tea - maybe very very good for you
Green tea, like black and oolong tea, comes from the Camellia senesis plant. For green tea, the plant leaves are steamed and parched after picking to prevent oxidation of the compounds present in the leaf. Green tea extracts have been used in traditional Chinese medicine for centuries but now conventional medicine practitioners are beginning to explore the health-promoting benefits of green tea derivatives.
The most common compound found in green tea is called EGCG (epigallocatechin-3-gallate ).
EGCG is a complex molecule with many potential anticarcinogenic functions. It acts as an antioxidant and neutralizes free radicals in the body. It also blocks angiogenesis, the process by which new blood vessels are formed and can block tumors from getting nutrients needed for growth. It inhibits cell cycles and has antibacterial properties. It can also protect against potential carcinogenic agents such as UV radiation and smoking by increasing the catabolism of these carcinogens.
Mayo Clinic Proceedings recently reviewed 400 studies on green tea and EGCG. They found only 15% of US adults drink green tea on any day. Therefore, most studies examining an association between green tea and lowered cancer risk have been conducted abroad, mainly in Asia. No prospective studies of green tea consumption and cancer risk have been reported from European or American subject populations and the studies reviewed had varied results. Unfortunately, differences in the methods used to assess green tea consumption make it difficult to derive any firm conclusions.
Although the study designs were variable, there were a number that did show green tea and EGCG may have potential as prevention or treatment for cancer and the biologic mechanisms of the compound make these findings compelling.
I am not aware of any prospective trials underway on green tea and that is a shame. We need trials that determine how the active ingredients in green tea interact with environmental and genetic factors. Although we have no proof... since it is readily available and non-toxic and it tastes good, maybe we should all be drinking a cup daily.
Posted by Toni Brayer, MD at 9:40 PM