What it is
Green tea is one of the world’s oldest and most popular beverages; the first recorded reference to tea dates back to A.D. 780. Green tea is made from the leaves of an evergreen shrub native to Asia. It contains more antioxidant compounds than other forms of tea because it is less processed. Black tea, for example, is made with dried, fermented leaves from the same plant.
Many cultures have appreciated the energizing lift that tea provides—in Asian religions, tea is used to maintain wakefulness during long meditations, and the English created their own ritual of afternoon tea soon after the beverage was introduced to their country in the mid-1600s. In Chinese medicine, tea has been used for thousands of years to treat diarrhea, colds, asthma, and headaches. Many Asians believe drinking tea promotes longevity.
Research during the past 20 years has triggered a surge of interest in green tea’s health benefits, particularly the potent antioxidant compounds that can provide protection against a wide range of diseases. Researchers have found that green tea may not only help prevent cancer and other degenerative diseases, but may also work as a natural weight loss aid.
How it works
Antioxidant compounds in green tea called polyphenols are responsible for the plant’s healing properties. These antioxidants neutralize free radicals, molecules that damage healthy cells. Free radicals are believed to be a primary cause of aging and degenerative diseases, including cardiovascular disease and cancer.
Of most interest to dieters is a polyphenol called epigallocatechin gallate (EGCG). EGCG appears to work by stimulating the body’s production of the hormone noradrenaline, which boosts the rate of metabolism, or calorie-burning.
In a small double-blind study reported in the American Journal of Clinical Nutrition (1999, vol. 70, no. 6), researchers at the University of Geneva tested the effect of green tea on weight loss. They gave ten healthy men (ranging from lean to mildly overweight) either a green tea supplement containing 90 mg of EGCG and 50 mg of caffeine, a supplement of 50 mg of caffeine, or a placebo with meals three times daily. During the study, the men ate a typical Western diet, didn’t restrict calories, and didn’t exercise. The researchers found that the green tea extract increased metabolism and energy usage by approximately 4 percent, while both the placebo and the caffeine alone had no effect.
Animal studies also support the use of green tea for weight loss. In one, Japanese researchers fed three groups of mice diets that contained 1 percent, 2 percent, or 4 percent green tea powder for 16 weeks. The researchers found that mice in the 2 percent and 4 percent groups gained less fat; in addition, those in the 4 percent group ate significantly less food than the other two groups (In Vivo, 2000, vol. 14, no. 4).
Unlike stimulant diet drugs, green tea doesn’t increase heart rate or trigger dangerous heart rhythm disturbances. Green tea does contain caffeine (though less than black tea) and can cause nervousness, insomnia, irritability, and headaches in people who are sensitive to caffeine. Generally, though, caffeine’s anxiety-producing effects are neutralized by green tea’s l-theanine. An amino acid found almost exclusively in tea plants, l-theanine acts like a neurotransmitter in the brain, increasing alertness while simultaneously inducing a state of relaxation.
You can readily buy decaffeinated green tea, but research indicates that the interaction of caffeine and polyphenols stimulates increased thermogenesis, or fat-burning.
How to take it
Green tea is widely available as a tea and in capsules, which are generally more potent. (You’ll get more polyphenols per cup with a good-quality green tea, available at some natural foods stores, or online at www.inpursuitoftea.com.)
An average dose is one cup of tea or one capsule with meals three times daily.
A box of 16 tea bags costs approximately $4; a bottle of 60 capsules is about $8.
Herbalist and author Laurel Vukovic lives in Ashland, Oregon, and has published nine books, including Herbal Healing Secrets for Women (Prentice Hall, 2000).