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Publix GreenWise Market Magazine - Spring 2009
Reading the Tea Leaves
 WHAT IT IS
Steeped in history, tea was reputedly discovered nearly 5,000 years ago by mythical Chinese emperor Shen-Nung, also known as the Divine Healer. Today it’s second only to water as the most-consumed beverage in the world. Both green and black varieties come from the Camellia sinensis plant. Black tea is fermented to produce its characteristic color and flavor, but green tea is not. The minimal processing means that green tea may retain more of its natural beneficial properties.
WHERE TO GET IT
Green tea is sold in tea bags, iced tea mixes and ready-to-drink iced teas. Supplements containing green tea extract are also readily available.
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THE EVIDENCE SO FAR
Green tea contains compounds that act as antioxidants. In cell cultures and animal models, “there is strong evidence that consumption of tea or its components can have a real and significant effect on cancer development,” says David Ringer, Ph.D., scientific program director at the American Cancer Society. To date, the evidence in humans remains unclear, but lab studies do suggest how green tea might help prevent or slow the growth of certain cancers.
First, antioxidant compounds “may help limit damage to DNA and proteins in the body,” says Ted Wilson, Ph.D., an associate professor of biology at Winona State University in Minnesota. “These same compounds may also help prevent the development of blood vessels that are critical for tumors to grow.” In addition, Wilson says, the compounds may inhibit cell division or promote cell death in cancer cells. Studies are now under way to determine whether the promising results translate into human health benefits, but Ringer says definitive answers from those studies “are probably five or more years away.”
THE JURY’S STILL OUT
Preliminary research suggests that green tea might help with weight control. In a recent study, researchers in Thailand randomly assigned 60 obese volunteers to take either green tea extract supplements or sugar pills for 12 weeks (Physiology & Behavior, February 2008). All study volunteers ate Thai food prepared by a hospital’s nutrition unit. Those in the green tea group lost more weight, possibly because their metabolism was revved up by the tea extract. But more and larger studies are needed before any firm conclusions can be drawn.
Some lab reports suggest that green tea might reduce skin cell damage caused by ultraviolet rays (Journal of Photochemistry and Photobiology B: Biology March/April 2008). And observations in humans hint that it also might help decrease cardiovascular deaths (Journal of the American Medical Association, September 2006) and age-related mental decline (The American Journal of Clinical Nutrition, February 2006). Time will tell whether these preliminary findings are borne out by more research.
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BOTTOM LINE
The amount of green tea needed to reap health rewards is still uncertain, but Wilson says “it would probably be a cup or two per day.” If you choose to go with supplements, a typical daily dose is 300 to 400 mg of green tea extract.
A cup of brewed green tea contains about 30 to 50 mg of caffeine. If you drink a lot, the caffeine could lead to restlessness, anxiety, headaches, trouble sleeping, nausea or frequent urination. Women who are pregnant or breast-feeding should be extra cautious, since caffeine can cross the placenta and be passed along in breast milk. In addition, drinking large amounts of green tea could reduce the absorption of certain medicines and iron supplements. Consult your physician.
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