[MOL] Tea Time for Cancer.... [02445] Medicine On Line


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[MOL] Tea Time for Cancer....



 
 
Tea Time for Cancer
by: Michael Guthrie, R. Ph.

It seems a lot more people are drinking tea these days, especially green tea. Recent research has found that green tea contains some very powerful antioxidants. It appears that the workhorses in green tea are a group of compounds known as polyphenols. Green tea is manufactured from fresh, unfermented tealeaves. This process leaves the catechins, potent antioxidants, intact. The most well researched catechin is epigallocatechin gallate.

The interest in green tea really took off when a number of studies were published demonstrating that populations that consumed green tea had significantly lower incidences of many kinds of cancer including breast, stomach, liver, pancreatic, lung, skin and esophogeal. Catechins in green tea appears to prevent cancer by at least six different mechanisms.


    1.They help to neutralize dietary carcinogens such as nitrosamine and aflatoxin.

    2.They interfere with the binding of cancer-causing agents to cellular DNA, thereby protecting cells against mutations that can eventually cause cancer.

    3.They protect against free-radical DNA damage that causes some cancers.

    4.They inhibit bacterial-induced DNA mutations that also can lead to certain cancers.

    5. They work with enzymes and other antioxidants in the intestine, liver and lungs to prevent the activation of certain carcinogens before they damage DNA.

    6.They protect against the effects of ionizing radiation and ultraviolet radiation.


One researcher found that mice given green tea were half as likely to contract cancer than controls when injected with human non-Hodgkins lymphoma cells. Remarkably the chemotherapeutic drug cyclophosphamide was not able to reduce the incidence at all! (Bertolini, 2000).

A couple of recent studies shed light on the possible mechanism by which green tea exerts its anti-cancer effects. First, it appears that green tea up-regulates a tumor suppressor gene called p21. This allows the cell to stop its uncontrolled growth (Liberto, 2000). Another study indicates that green tea down-regulates NF Kappa B, a complex that contributes to uncontrolled cell growth. This allowed cancer cells to commit programmed cell death (Ahmad, 2000). A recent study done at the Karolinska Institute in Stockholm found another anti-cancer activity of green tea. It suppresses angiogenesis, which is the process of laying down blood vessels by cancer cells (Cao, 1999). Cancer cells depend on angiogenesis to form tumors. Still, another study found further anti-cancer activity with green tea. The study, done in Japan, found that epigallocatechin gallate (one of the main constituents of green tea), inhibits the secretions of collagenases. This deprives the cancer cells of a mechanism required for invasion of adjacent tissues (Sazuka, 1997).

Special benefits in prostate cancer: Two of the catechins in green tea have been found to be effective inhibitors of an enzyme that converts testosterone to dihydrotestosterone. Pharmaceutical products that have this effect have been shown to be effective in preventing prostate cancer (Liao, 1995).

One exciting finding about green tea has to do with its effect on telomerases. Telomeres are the genetic way of saying "the end" to cell division. In other words, a cell can only divide so many times. Cancer cells produce telomerases which destroy the telomeres allowing the cancer to divide without end (Naasani, et al, 1998). Still another finding with green tea is its suppression of a growth factor enzyme known as quinol oxidase (NOX). While expressed in normal cells while dividing, it is always expressed in cancer cells where it is called t-NOX. The researchers found that when exposed to the active ingredients in green tea, the cancer cells were unable to grow after division, and went into apoptosis (programmed cell death) (Moore, 1998).

 
 
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