This study was designed to see if green tea catechin concentrate had any effect on the levels of GST enzymes in healthy individuals − research that could explain the teas anti-cancer properties. Healthy volunteers were asked to abstain from consuming any tea or tea-related products for four weeks. At the end of this washout period, blood was drawn and baseline GST enzyme levels were determined for each participant. Then, the volunteers were asked to take four Polyphenon E capsules, for a total of 800 milligrams of EGCG, each morning on an empty stomach for four weeks and to abstain from drinking tea or eating many cruciferous vegetables, which contain other beneficial chemicals. Another blood sample was taken after four weeks, and GST activity was determined.
Researchers found that use of Polyphenon E enhanced GST activity when data from all participants were included for analysis. But it had its most significant effect in volunteers whose baseline blood measurements showed low GST activity − an 80 percent increase compared to baseline GST activity. Activity did not change in volunteers with medium GST expression, or in those with the highest levels, GST seemed to decrease slightly although researchers believe that decline was due to random variation.
This is the first clinical study to show proof that chemicals in green tea can increase detoxification enzymes in humans, Chow said. There may be other mechanism in play by which green tea may protect against cancer development, but this is a good place to start.
|Contact: Greg Lester|
American Association for Cancer Research