An old remedy, but not everyone’s cup of tea

The Camellia sinensis plant was first cultivated in China and is now grown throughout Asia and in parts of Africa. Green tea is made from the plant’s stems and leaves, which also are used to make black and oolong tea, though processing makes the teas chemically distinct. Green tea has a high concentration of polyphenols, compounds with strong antioxidant properties that scientists believe may help protect against some types of cancer.

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Uses: The Chinese have consumed green tea for thousands of years and have attributed to it many health benefits, including the treatment of headaches, nausea and diarrhea. Today, some people take green tea extract in supplement form, believing that it may help ward off cancer and heart disease.

Dose: 100 milligrams to 500 milligrams a day of green tea extract, available in capsules. One cup of brewed tea provides the same amount of polyphenols as a 100-milligram capsule of green tea extract.

Precautions: Green tea is about 2% to 4% caffeine -- less than a cup of coffee. Most of green tea’s possible side effects, including restlessness, insomnia and increased heart rate, are attributed to caffeine. In infants, green tea may impair iron metabolism. Pregnant women should limit their intake because high doses of caffeine may harm developing fetuses. Large amounts of green tea also may upset the stomach.

Research: Little research has been done on the effectiveness of green tea supplements in humans, but preliminary research suggests that drinking green tea as a beverage may help prevent several forms of cancer, including breast, lung, stomach and colon cancer. Researchers continue to study the effects of green tea extract on prostate cancer and other forms of the disease. Studies also have shown that green tea may be helpful in reducing the risk of heart disease and stroke, promoting weight loss and preventing cavities.

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Dietary supplement makers are not required by the U.S. government to demonstrate that their products are safe or effective. Ask your health-care provider for advice on selecting a brand.

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-- Elena Conis