Green light for green tea

by Marla Hardee Milling

In 1211 A.D., the monk Eisai wrote the following in his book Maintaining Health by Drinking Tea:

"Tea is a miraculous medicine for the maintenance of health. Tea has an extraordinary power to prolong life."

More than 700 years later, his words are still relevant. But now, they are supported by medical research. Preliminary work continues to prove that green tea does enhance a person's health.

A hot cup of green tea can be relaxing, soothing, and can even help you sleep. Now, there's more evidence that green tea might be instrumental in preventing cancer. In fact, the results are so encouraging that the old adage "An apple a day keeps the doctor away" might be better stated: "Four cups of green tea a day keeps the oncologist away."

Cancer prevention powers

Purdue University researchers Dorothy and D. James Morre recently found that EGCg—a compound in green tea—inhibits an enzyme needed for cancer cells to grow and can kill cultured cancer cells with no ill effect on healthy cells. Morre and her husband, who is the Dow Distinguished Professor of Medicinal Chemistry and Molecular Pharmacology at Purdue, have shown how green tea interferes with this enzyme that is necessary for the growth of many types of cancer cells, including breast, prostate, colon and neuroblastoma.

"Our work has focused on a specific protein of the cancer cell surface that is inhibited by EGCg. In combination with other tea catechins, this protein may relate to an ability of green tea to slow the growth of cancer cells," says Dr. Dorothy Morre, professor of foods and nutrition in Purdue's School of Consumer and Family Sciences.

Their findings suggest that consuming more than four cups of green tea a day could provide enough of the active compound to slow and prevent the growth of cancer cells. "For this response, tea with or without caffeine is equivalent and can be taken either hot or cold," says Morre.

The research continues

"Both green and black tea have been found to inhibit cancer formation in many animal studies," says Dr. Allan H. Conney, chairman of the College of Pharmacy at Rutgers University and director of the Laboratory for Cancer Research. "In addition to the cancer prevention activity of tea in animals, either green or black tea inhibits tumor growth in tumor-bearing mice."

"The most recent studies indicate that people drinking green tea have a lower risk of developing stomach or esophageal cancer," continues Dr. Conney. "But the amounts of green tea ingested in these later studies were more than five cups a day. These studies were done in Japan and in China, in people who had a high risk for developing stomach or esophageal cancer. Although the data demonstrate that green and black tea have cancer chemopreventive activity in animals, there is still a need for more studies in humans."

Why green tea packs a bigger punch

While both green and black tea offer health benefits, green tea packs a bigger punch in terms of health benefits. That's because of a difference in the way the tea is produced.

All varieties of tea are derived from the same plant, Camellia sinensis. The difference, however, is in the way the tea leaves are processed after they are picked. For black tea, freshly picked leaves are rolled and then withered indoors, which causes most of the active substances in the leaves to oxidize. For green tea, the leaves are steamed to preserve the natural active substances of the leaf.

Tea is a powerful antioxidant

It's known that fruits and vegetables are essential to a healthy diet because they are filled with antioxidants. But now, researchers are finding that the flavonoids in tea have a greater antioxidant effect than single servings of many vegetables and fruits, including broccoli, carrots, apples and grapes. Green tea should not be used as a substitute to eating a diet rich in fruits and vegetables, but it will add beneficial antioxidants as part of a nutritious diet.

"Tea flavonoids function as antioxidants similar to vitamins C and E; however, the components in black and green tea appear to be more potent than in those vitamins, based on in vitro and animal studies," says James Klaunig, Ph.D., professor and director of toxicology at Indiana University.

Other health benefits

Cancer prevention is just one of many possible benefits that come from drinking green tea. Green tea is also getting gold stars from researchers for reducing the risk of heart disease and stroke, improving the circulatory system by reducing the risk of blood clots, fighting the influenza virus, and killing bacteria that might lead to food poisoning or diarrhea, if left alone. And, green tea is touted for helping people stay refreshed and mentally balanced, without any known side effects.

Drinking green tea may also keep you free from the dentist's drill. Green tea contains a natural fluoride that helps prevent cavities and strengthens tooth enamel. It also helps eliminate oral bacteria that can lead to halitosis (bad breath).

Raise your glass to a healthy habit

While research continues on cancer prevention and other health benefits, tea remains an excellent beverage choice. Fresh-brewed green tea is 100% natural, and contains no fat, calories, alcohol or sugar (if you leave it unsweetened.) Also, a cup of green tea has about half the caffeine found in a comparable cup of coffee. So do your body good...drink up!