Big Green Cancer-Fighting Machine
Big Green Cancer-Fighting Machine
The things we do to mice.
Researchers at the University of South Carolina treated mice with a chemical that induces colon cancer. Then, when the mice were two months old, half were given water to drink, while the other half drank a solution of green tea for about eight weeks. Results showed that the number of new colon tumors was significantly lower in the green tea group, although there was no difference in tumors that already existed when the intervention began.
The USC researchers note that these results, while promising, don’t imply that tea drinking among humans would produce the same results. But another green tea study, just published, shows that an extract of this popular tea may produce very beneficial results in the human immune system.
Toxin buster
About one-third of the dry weight of green tea leaves is made up of antioxidant flavonoids called catechins. These flavonoids are believed to activate a major group of detoxification enzymes known as GST, which play a large part in protecting the body against toxic compounds that cause cancer.
To test the effect of green tea on GST levels, researchers at the Arizona Cancer Center at the University of Arizona asked 42 healthy subjects to avoid all tea products for four weeks. Before intervention began, fasting blood samples were collected from each subject and GST levels were measured. Then, for another four weeks, each subject received a green tea extract that contained 800 mg of epigallocatechin gallate (EGCG).
EGCG is the most abundant of the four types of green tea catechins, and is the component of green tea that has been shown to inhibit tumor cell growth.
Another blood test was conducted after the intervention period. Analysis showed that subjects who had the lowest levels of GST before intervention increased their GST levels by 80 percent on average. Subjects who began the intervention with higher GST levels showed little or no increase.
Writing in the August 2007 issue of Cancer Epidemiology Biomarkers & Prevention, the authors note that GST levels can be compromised by genetic or environmental factors.
A warning comes with it
GST are not the only enzymes affected by EGCG.
More than two years ago I told you about a UK study in which researchers tested the effect of EGCG on an enzyme called dihydrofolate reductase (DHFR), which promotes cancer cell growth by producing new DNA in cancer cells. The test revealed that EGCG levels found in tissue and blood samples of green tea drinkers was sufficient to effectively bind DHFR, inhibit cell growth, and induce apoptosis, which is a series of reactions that cause cancer cells to self destruct.
But the UK team also discovered a potential drawback to EGCG supplementation: High levels of EGCG may reduce folate levels. And as we saw in yesterday’s e-Alert (“Feels Like Summer” 9/4/07), folate is a key nutrient that protects the heart, reduces stroke risk, helps relieve depression, and may significantly lower the risk of breast cancer.
The average green tea drinker can address the folate problem by increasing dietary sources of folate (chicken liver, lentils, asparagus and spinach) and by taking a folic acid supplement. Pregnant women, however, should be especially cautious because low folate levels increase the risk of causing neural tube disorders to unborn children. People with cardiovascular problems also need to make a concerted effort to keep folate levels high.
Talk to your doctor before adding green tea extract or a folic acid supplement to your daily regimen.
Sources:
“Green Tea May Stop Colon Cancer in its Tracks – Study” Stephen Daniells, NutraIngredients-USA, 9/8/07, nutraingredients-usa.com
“Modulation of Human Glutathione S-Transferases by Polyphenon E Intervention” Cancer Epidemiology Biomarkers & Prevention, Vol. 16, No. 8, August 2007, cebp.aacrjournals.org
“The Antifolate Activity of Tea Catechins” Cancer Research, Vol. 65, No. 6, 3/15/05, cancerres.aacrjournals.org
