Green tea | Green tea cancer prevantion & Researches

                           Green tea preventing from  cancer

                                              

      •  The healing properties of green tea have shown to have some very, very encouraging results on people with all types of cancer. Several population-based studies have shown that green tea helps protect against cancer.
      •  Green tea is a very powerful weapon against preventing cancer and even reducing the growth of cancer cells. Laboratory cell culture studies show that green tea polyphenols are powerful triggers of apoptosis (cell suicide) and cell cycle arrest in cancerous but not in normal cells.
      •  Cell cycling is the process cells go through to divide and replicate. These anticancer actions have been assumed to be due to the powerful antioxidant effects of green tea’s catechins, especially epigallocatechin-3-gallate (EGCG).
    • This is a reasonable assumption, given that a number of studies have shown that green tea possesses remarkable antioxidant properties. In one study published in the November 2004 issue of Mutation Research, EGCG’s protective antioxidant effects against several carcinogens were found to be 120% stronger than those of vitamin C.5
    • But while green tea’s antioxidant prowess is impressive, recent studies show it is far from the only way in which this multi-talented beverage protects us against cancer. One of these mechanisms is green tea’s ability to inhibit angiogenesis, the development of new blood vessels.
    •  Cancer cells, which are constantly attempting to divide and spread, have an endless appetite that can only be temporarily quieted by increasing the number of blood vessels that supply them with nutrients.
    • By inhibiting angiogenesis, green tea helps starve cancer. Studies also show that green tea works at the genetic level, shutting off genes in cancerous cells that are involved in cell growth, while turning on those that instruct the cancer cells to self-destruct.9
    • Green tea’s anticancer effects include its ability to inhibit the overproduction of the enzyme cyclooxygenase (COX)-2, a protein whose overproduction has been implicated as a factor in many diseases, including arthritis and cancer. COX-2 has an enzyme counterpart, called COX-1, which may be helpful to leave untouched when preventing overproduction of COX-2. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen (which inhibit both COX-1 as well as COX-2), and specific COX-2 inhibitors such as Vioxx and Celebrex (which inhibit only COX-2), have been considered as possible agents in the prevention of some forms of cancer,
    • But their severe toxic side effects on normal cells limit their usefulness. In studies of prostate cancer cells, EGCG appears to block only COX-2 and to have no negative side effects.
    •  ECGC, a catechin present in green tea in amounts about 5 times higher than in black tea, inhibits the enzyme dihydrofolate reductase (DHFR), which cancer cells need to be able to grow, and which is a well recognized target of anti-cancer drugs.
    •  Scientists decided to look at ECGC after they realized the green tea catechin looks a lot like the cancer drug methotrexate, which prevents cancer cells from making DNA by inhibiting the DHFR enzyme. They discovered that ECGC kills cancer cells in the same way as the drug. Although ECGC binds strongly to DHFR, which is essential in both healthy and cancerous cells, it does not bind as tightly as methotrexate, so its side effects on healthy cells are less severe than those of the drug. ECGC’s binding to DHFR may also explain .
    • women who drink large amounts of green tea around the time they conceive and early in their pregnancy may have an increased risk of having a child with spina bifida or other neural tube disorders. In the fight against cancer, green tea polyphenols are team players, helping cancer-killing drugs do their job.g5




  • In a study published in the October 2004 issue of the Journal of Pharmacy and Pharmacology, green tea polyphenols caused drug-resistant cancer cells, which were able to extrude or push out one of the most commonly used cancer drugs, doxorubicin, to retain the drug, which could then destroy them.
  • In addition, another study published in the August 2004 issue of Cancer Letters, found that another compound in green tea, the amino acid theanine, reduces the negative side effects of doxorubicin by increasing the level of one of the body’s most important internally produced antioxidants, glutathione, in normal tissues in the liver and heart-but not in tumors.




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