•  Breast Cancer

Both green and black teas come from the tea plant, Camellia sinensis, a fragrant evergreen shrub that thrives in China and India. The differences in taste and aroma arise from the way the leaves are processed. Leaves for black tea are fermented and then fired black in an oven; green-tea leaves are simply steamed and dried. That's why green tea tastes lighter and grassier. Green tea is getting attention these days because many studies suggest that drinking a few cups a day may help prevent certain cancers.

When researchers compared groups of people who regularly drank green tea to those who didn't, the tea-drinkers had lower rates of bladder, esophageal, pancreatic, and recurrent breast cancers. However, the evidence for a protective effect against stomach cancer is conflicting. One population study also suggested that drinking green tea regularly might help lower cholesterol levels. Researchers say they need to confirm these findings in large clinical trials before they can be sure that the tea was responsible for those results. In one human study, green tea helped treat oral leukoplakia (sores in the mouth that are often pre-cancerous). And early human research showed that green tea applied to the skin might help reduce or prevent sunburns.

Green tea is loaded with powerful antioxidants called polyphenols that protect cells from the ravages of oxidation, a chemical reaction that can lead to cancer and the hardened arteries that cause heart disease. In fact, researchers at the University of Kansas say that one antioxidant, a tongue-twister called epigallocatechin gallate, or EGCG, is 25 times more effective in laboratory tests than the much-touted vitamin E at helping cells resist the damage caused by oxidation and helping damaged cells repair themselves. Both black and green teas have the same total polyphenol content, but green tea has about twice the EGCG.

The warmth and steam from any hot beverage can help you breathe easier if you're congested or have mild asthma. All teas also contain a relative of caffeine called theophylline, a mild stimulant that helps dilate the bronchial tubes in the lungs. In fact, theophylline is an ingredient in many prescription and over-the-counter asthma drugs. However, tea won't help lessen a severe asthma attack; use your medication or see a doctor immediately.

Green tea generally contains about half as much caffeine as regular black tea (about 60 milligrams per 6-ounce cup). If you're sensitive to caffeine, drinking several cups a day may cause stomach upset, irritability, increased heart rate, or difficulty sleeping. Children may be more sensitive to caffeine than adults. Pregnant women should limit their caffeine intake and nursing women should avoid it altogether.

If you're trying to get health benefits from tea, you'll probably do best drinking it regularly, preferably several times a day. If you don't like the taste of tea or want to avoid the caffeine, green tea supplements are available in pharmacies and health-food stores. Some green tea supplements provide nearly the same amount of antioxidant polyphenols as four cups of green tea. However, few studies have used these products so we don't know if they have the same effect as drinking green tea. Be aware that the government doesn't regulate herbal supplements, so quality and potency can vary from product to product.

Further Resources

Varro E. Tyler, PhD. Herbs of Choice: The Therapeutic Use of Phytomedicinals. Pharmaceutical Products Press, 1994.

Andrew Weil, M.D. Natural Health, Natural Medicine. Houghton Mifflin, 1995, 1998.

References

First published September 3, 1998
Last updated January 23, 2008
Copyright © 1998 Consumer Health Interactive and OneBody, Inc.

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