Active constituents: Green tea contains volatile oils, vitamins, minerals, and caffeine, but the active constituents are polyphenols, particularly the catechin called epigallocatechin gallate (EGCG). The polyphenols are believed to be responsible for most of green tea's roles in promoting good health¹.

Research demonstrates that green tea guards against cardiovascular disease in many ways. Green tea lowers total cholesterol levels and improves the cholesterol profile (the ratio of LDL cholesterol to HDL cholesterol), reduces platelet aggregation, and lowers blood pressure ^2,3,4,5. The polyphenols in green tea have also been shown to lessen the risk of cancers of several sites, stimulate the production of several immune system cells, and have anti-bacterial properties -- even against the bacteria that cause dental plaque^6,7,8.

Researchers at the USC/Norris Comprehensive Cancer Center in Los Angeles and the Shanghai Cancer Institute in China report that compounds known as polyphenols, found in great abundance in green tea, have protective effects against the development of esophageal and gastric cancer.

"In our study, we found that men who drank green tea reduced their risk of esophageal cancer and gastric cancer by as much as 50 percent, and that the tea was most protective in those men who were deficient in other antioxidants," says lead author Dr. Can Lan Sun.

Antioxidants are a group of nutrients believed to protect the body from cancer-causing elements in the environment, such as cigarette smoke. Polyphenols are one type of antioxidant, which are found not only in green tea, but also black tea, grapes, wine, chocolate, and a variety of plant based foods.

In this study, researchers examined urinary levels of epigallocatechin (EGC) and epicatechin (EC), two chemical markers of polyphenols which reflect tea intake. They measured levels in 190 men with gastric cancer, 42 with esophageal cancer, and 772 men who were cancer free. All were residents of Shanghai, where the rate of gastric and esophageal cancer is among the highest in the world.

After comparing test results of all the men, scientists report those with the highest levels of EGC in their urine indicating the greatest intake of green tea had what researchers call a "statistically significant" reduction in gastric and esophageal cancer. Interestingly, that reduction was greatest in those men who also had low levels of carotene another potent antioxidant.

"Our study seems to indicate that the polyphenols in green tea may be especially protective in those who have low levels of other antioxidants, and in this way may help protect against cancer," Sun says.

For Heller, the most important finding is a reaffirmation of the need for adequate intake of foods high in antioxidants. "The best way to ensure that our bodies are getting the protective health benefits of these compounds and many others contained in plants, is to eat a diet very high in vegetables, whole grains, legumes and fruit and drink some green tea, " Heller says.

Green Tea Supplement Helps Prevents Prostate Cancer in High-Risk Men - American Association for Cancer Research, April 20, 2005 - Researchers believe green tea catechins have powerful antioxidant properties. A supplement containing antioxidants from green tea was 90 percent effective in preventing prostate cancer in men at high risk for the disease.

There are many benefits to drinking green tea, but you'll need to drink 12 cups a day to get the amount of catehins consumed in the study.

That's the conclusion of an Italian study that found after a year of taking green tea catechins, only one man in a group of 32 who were at higher risk of prostate cancer actually developed the disease, while nine men in a group of 30 high-risk men who took a placebo developed prostate cancer.

"To our knowledge, this is the first study showing that green tea catechins (GTC) have potent chemoprevention activity for human prostate cancer," said study author Saverio Bettuzzi, an associate professor of biochemistry in the School of Medicine at the University of Parma in Italy.

Findings from the study were presented April 20 at the American Association for Cancer Research annual meeting, in Anaheim, Calif.

TUESDAY, April 16 (HealthScoutNews) -- If a group of Chinese researchers are right, green tea may offer important protection against Parkinson's disease -- a neurodegenerative disorder that made headlines when it was diagnosed in both actor Michael J. Fox and boxing legend Muhammad Ali.

The new finding, reported today at the annual meeting of the American Academy of Neurology in Denver, explains how ingredients plentiful in green tea can help the flow of a brain chemical that's at the heart of this devastating disease.

"In our study, we demonstrate the inhibitory effects of green tea polyphenols," on mechanisms directly involved in Parkinson's disease, says study author Dr. Tianhong Pan, a researcher from China who was working at Baylor College of Medicine in Houston during the study.

Pan says she and her colleagues in China began the animal study a joint effort between the National Cancer Institute and the Chinese government because of the lower rates of Parkinson's disease among populations where green tea is heavily consumed.

"The prevalence of Parkinson's disease was lowest in Asia and Africa, where green tea is commonly consumed, so it seems that there is some relationship between green tea consumption and the occurrence of [this disease]," Pan says. For neurologist Dr. Souhel Najjar, this is the first research to document the mechanism by which green tea can protect the brain.

"That mechanism involves the transport of the brain chemical dopamine, which plays a key role in Parkinson's disease," says Najjar, a Parkinson's disease specialist. Proving green tea can work on that transport system could be key to learning how to prevent the disease, Najjar says, who adds it could also open the door to new treatment strategies. Pan agrees: "The results suggest that green tea may have potential both in the treatment and protective effects in Parkinson's disease." The mechanism explored in this study involved the transport of dopamine from the area of the brain where it is made to a second area where it is utilized, movement that is critical in Parkinson's disease.

"Normally, dopamine is made an area of the brain called the substantia nigra, and it travels a pathway to a second area of the brain known as the striatum," Najjar says. Sometimes, however, too much of the dopamine flows back into the substantia nigra. That leaves the striatum with less dopamine than it needs to function properly.
Because dopamine helps muscles move smoothly and efficiently, when a deficiency occurs, symptoms of Parkinson's develop including muscle rigidity and tremors.

In the new study, however, researchers demonstrated that compounds known as polyphenols can block the back flow of dopamine, so the transport continues, unhampered, from one area of the brain to the other.
"By keeping the transport of dopamine from being disrupted, polyphenols might be able to reduce the risk of Parkinson's disease, as well as reduce the progression of the disease in those already affected, " Najjar says.
Although both doctors are optimistic, no one is certain the results will apply to humans. Pan's group tested levels of dopamine in mice, and then treated some with polyphenols while leaving others untreated. They then injured the specific neurons or brain cells linked to Parkinson's disease in all of the mice, and measured dopamine levels again.

The result: Those mice treated with polyphenols appeared to be protected from the assault on brain cells. Pan reports polyphenols were able to "inhibit the uptake of dopamine by blocking the dopamine transporter."

"In this way, green tea may serve to protect against Parkinson's, particularly in the face of toxic elements that may be linked to this disease," Najjar says.

However, can drinking green tea help people as much as it helps mice?

"Although green tea polyphenols have numerous biological effects in vitro, and epidemiological studies have shown some health benefits in tea consumption, what is not clear at this time is whether pharmacologically effective doses of green tea polyphenols can be attained in blood or tissues simply by consuming tea infusions," Pan says.

Najjar says it's possible, but based on this study "there is not enough evidence to make any kind of recommendation."

In addition to green tea, polyphenols are found in black tea, grapes, red wine, chocolate and other plant sources.

To learn more about Parkinson's disease, you can visit the Parkinson's Disease Foundation - www.pdf.org/index.cfm

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