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2 Green Tea
Both green tea and black tea are derived from the same plant, Camellia sinensis. Green tea is produced by lightly steaming the freshly cut leaves, while to produce black tea the leaves are allowed to oxidize. Oolong tea is partially oxidized. During oxidation, enzymes present in the tea convert polyphenols, which possess outstanding therapeutic action, to compounds with much less activity. With green tea, oxidation is not allowed to take place because the steaming process inactivates these enzymes. Green tea is very high in polyphenols with potent antioxidant and anticancer properties.The major polyphenols in green tea are flavonoids (e.g., catechin, epicatechin, epicatechin gallate, epigallocatechin gallate, and proanthocyanidins). Epigallocatechin gallate is viewed as the most significant active component. Green tea also contains caffeine at about 30 to 50 mg per cup.
Green Tea Antioxidant Supplements
Green tea polyphenols are potent antioxidant compounds that have demonstrated greater antioxidant protection than vitamins C and E in most but not all experimental studies. In addition to exerting antioxidant activity on its own, green tea may in-crease the activity of antioxidant enzymes in the small intestine, liver, and lungs. The ability of green tea extract to protect against oxidative damage to LDL cholesterol indicates that it may protect against atherosclerosis and heart disease.
Green Tea and Cancer Prevention
Population studies have demonstrated that green tea consumption may be one of the major reasons why the cancer rate is lower in Japan. A number of experiments conducted in test tube and animal cancer models have shown that green tea polyphenols inhibit cancer by blocking the formation of cancer-causing compounds such as nitrosamines, suppressing the activation of carcinogens, and detoxifying or trapping cancer-causing agents. The forms of cancer that appear to be best prevented by green tea are cancers of the gastrointestinal tract, including cancers of the stomach, small intestine, pancreas, and colon; lung cancer; and estrogen-related cancers, including most breast cancers. These preliminary results need confirmation in double-blind studies in humans.
Green Tea Available Forms
Green tea is most often consumed as a beverage from either loose green tea leaves or tea bags. Green tea extracts concentrated for polyphenol content (e.g., 70-80 percent) are available, including decaffeinated versions.
Green Tea Warnings
Do not exceed the recommended dosage of caffeine or caffeine-containing herb, especially if combined with other plant stimulants such as ephedrine.
Caffeine may have the potential to cause cardiac arrhythmia (irregular heartbeat). As a precaution, it is recommended that caffeine be avoided by individuals with a history of cardiac arrhythmia and/or palpitations and during the first month after suffering a heart attack.Chronic caffeine consumption can lead to physical and psychological dependence. If caffeine intake is stopped abruptly, physical signs of withdrawal may occur. The most common symptoms of caffeine withdrawal are fatigue and headache. These symptoms usually begin twelve to twenty-four hours after caffeine intake is stopped and may last as long as a week.
Green Tea Side Effects
As with any caffeine-containing beverage, overconsumption of green tea or caffeine-containing green tea extract may produce a stimulant effect (nervousness, anxiety, insomnia, irritability). Other possible side effects include light-headedness, headache, nausea, gastric irritation, and vomiting. The breakdown of caffeine is inhibited by the following drugs: birth control pills, estrogen (e.g., Premarin), mexiletine, cimetidine (Tagamet), and various antibiotics (e.g., norfloxacin, enoxacin, and ciprofloxacin). Tricyclic antidepressant drugs, ephedrine, and theophylline (used in asthma) all potentiate the effects of caffeina. Alcohol inhibits the breakdown of caffeine. To avoid the potential danger of caffeine overdose, be aware of your consumption of caffeine-containing foods and beverages. Doses of caffeine over 250 mg can produce definite signs of toxicity, such as stomach pain, nervousness, increased heart rate, elevation in blood pressure, frequent urination, and disordered thought and speech. More serious symptoms include arrhythmia {irregular heartbeat) and seizures.
Even if the victim is not displaying any of the symptoms above, do the following in case of accidental overdose: If the victim is unconscious or having convulsions, call for an ambulance immediately. If you take the victim to an emergency room, be sure to bring the bottle or container with you. If the victim is conscious, call your local poison control center or a health care professional. The poison control center may suggest inducing vomiting with ipecac syrup (available without a prescription at any pharmacy). Do not induce vomiting unless specifically instructed to do so. Caffeine consumption, even from green tea, is best avoided during pregnancy and lactation. Caffeine has long been suspected of causing malformations in the fetus, although this is controversial. The dosage required for this effect is probably quite large, but the data are scant, as experimentation on humans is not feasible. Caffeine has been shown to cause malformations in rats when ingested at rates comparable to seventy cups a day for humans. In humans, daily doses of 300 mg per day or more in pregnant women have been linked to slowed growth and low birth weight of the infant.
Caffeine passes into breast milk and may cause wakefulness and irritability in nursing infants. There does not appear to be any appropriate use of caffeine or caffeine-containing beverages in children. The adverse effects of caffeine are usually more severe in children because their breakdown of caffeine is slower than that of adults.
Seniors are often more sensitive to caffeine's stimulant effects and may be more likely to experience nervousness, anxiety, and insomnia. Seniors are also more likely to be taking drugs that interact with caffeine