Envy with Green
If you’re one of those who have read about the many benefits of green tea over the past few years and have gone out of your way to include a cup or two in your daily routine, then I have some information today that will make you feel even better about your beverage choice.
Denying the receptor
We’ll start with a Japanese study published just last month.
Researchers at Kyushu University in Japan set out to examine the means by which green tea has been shown to help protect against several cancers, such as breast and prostate cancer. About one third of the dry weight of green tea leaves is made up of a flavonoid called catechin. And the most abundant of the four types of green tea catechins is epigallocatechin gallate (EGCG), which also happens to be the component of green tea that has been shown to inhibit tumor cell growth.
In trying to understand the mechanism that makes EGCG effective, the Kyushu Team focused its attention on a type of cancer receptor cell known as 67 LR. Many cancer tumors produce large amounts of this cell, which senses chemicals and responds with electrical signals. Scientists believe that 67 LR is one of the key agents that helps cancer spread throughout the body. Using lung cancer cells, the researchers observed that cell growth was inhibited by exposure to EGCG at concentrations that would equal just three cups of green tea.
Quite honestly, the chemical details of this study were over my head, but the conclusion is clear: The Kyushu researchers believe their work reveals that EGCG binds to 67 LR cells and prevents them from prompting tumor growth.
Cutting off the supply
Just days after the Kyushu study was released, another study of EGCG was reported in the journal, Blood. Researchers from the Mayo clinic in Rochester, Minnesota, examined the interaction between EGCG from green tea and cancer cells taken from 10 patients diagnosed with the most common type of leukemia: B-cell chronic lymphocytic leukemia (CLL).
Again, I won’t try to explain the complex chemistry at work here, except to note that this research also involved a receptor cell, called VEGF, which nurtures growth in leukemia. Researchers found that EGCG suppressed the VEGF mechanism, inhibiting the growth of new blood vessels necessary for cancer proliferation. In 8 of the 10 samples, EGCG prompted the death of cancer cells.
Researchers hope their study will eventually lead to a non- toxic way to treat CLL. This type of leukemia can only be treated with chemotherapy, but when older patients are diagnosed with early stages of CLL (a cancer that mostly affects people over the age of 60), some doctors choose to monitor the slow-growing disease before subjecting a patient to unnecessary (and harsh) treatments. The Mayo team believes that EGCG could be an effective, low-impact treatment for early stage CLL.
Tea time in LA
Although the interest in green tea as a benefit to health has only become popular in the West over the past decade, for more than 30 years, Western researchers have known that the frequency of solid tumor cancers is far lower in countries where populations consume large amounts of green tea. Solid tumor cancers include lung, gastrointestinal and breast cancers.
In the e-Alert “Keep it Green” (10/7/03), I told you about a study that took the research of green tea out of the laboratory and into the homes of more than 1,000 women, with surprising and promising results concerning the prevention of breast cancer.
A team of researchers from the Department of Preventive Medicine at the University of Southern California (USC) interviewed almost 1,100 Asian American women (aged 25 to 74) living in Los Angeles. 501 women had been diagnosed with breast cancer, and 594 were cancer-free.
Between 1995 and 1998, each subject was interviewed in person to determine a wide variety of factors, including food and beverage intake, personal medical history, family health history, and general lifestyle details such as smoking habits and alcohol intake. An examination of the data showed that women in the non-cancer group were much more likely to be regular green tea drinkers. In fact, on average, those who drank at least 8.5 milliliters (less than half a cup) of green tea each day, had a reduced breast cancer risk of nearly 30 percent. Those who consumed more than 8.5 milliliters reduced their risk even more.
This benefit was found only with green tea consumption. Women who regularly drank black tea didn’t reduce their breast cancer risk.
Put away the tea bucket
These studies are somewhat unusual among typical green tea research. Most often the results imply that health benefits of green tea require a daily intake of a dozen cups or more. I enjoy green tea as much as the next guy, but like most people, I’m not inclined to drink a bucketful each day. Which is one of the reasons, no doubt, why we’re seeing more green tea extracts on the market. And while the extracts may provide benefits, it appears that just a few daily cups of the real thing might be doing a world of good.
Sources:
“A Receptor for Green Tea Polyphenol EGCG” Nature Structural and Molecular Biology, Vol. 11, 2004, nature.com
“Green Tea Mechanism Revealed” NutraIngredients.com, 3/26/04, nutraingredients.com
“VEGF Receptor Phosphorylation Status and Apoptosis is Modulated by a Green Tea Component, Epigallocatechin-3- gallate (EGCG) in B cell Chronic Lymphocytic Leukemia” Blood, 3/2/04, ncbi.nlm.nih.gov
“Green Tea May Fight Leukemia” NutraIngredients.com, 4/1/04, nutraingredients.com
“Green tea and risk of breast cancer in Asian Americans” International Journal of Cancer, Vol. 106, No. 4, 574-579, 9/10/03, interscience.wiley.com
“Another Green that Might Prevent Breast Cancer” Janet Raloff, Science News, Vol. 164, No. 11, 9/13/03, sciencenews.org