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Green Tea
Read other articles about Green Tea.
Latin name: Camellia sinensis (Theaceae [tea] family)
GENERAL DESCRIPTION
A native of the rainy forests of Southeast Asia, the tea plant is cultivated in Burma, China, India, Japan, Turkey, Pakistan, Malawi, Argentina, Georgia, Sri Lanka, and Africa. The evergreen leaves are limp and downy when young, thick and rounded when mature. In the wild, this small tree grows many small branches. Cultivated tea plants are regularly pruned and kept to a height of about five feet (150 centimeters) to make harvesting easy. Only the leaf buds and young leaves are harvested, by hand, to make tea.
Green tea and black tea (the more familiar beverage type of tea) come from the same plant, but green tea is less processed so more of the original plant substances survive in this herb. Green tea contains high levels of substances called polyphenols, which are known to have strong antioxidant, anticarcinogenic, antitumorigenic, and antibiotic properties.
EVIDENCE OF BENEFIT
Green tea is both a stimulant and an antioxidant with a diversity of healing applications. The polyphenols in green tea are potent antioxidants. Researchers have found that one of the polyphenols, designated epigallocatechin gallate (EGCG), is over 200 times more powerful than the renowned antioxidant vitamin E in neutralizing free radicals. Also, green tea increases energy, which may make it useful as part of a weight-loss program.
Benefits of green tea for specific health conditions include the following:
• Asthma. Theophylline, a chemical found in both green and black tea, is extracted from the leaf of the tea plant. Theophylline relaxes the smooth muscles supporting the bronchial tubes, reducing the severity of asthma and bronchitis. Drinking either green or black tea provides theophylline in doses large enough to affect asthma.
• Atherosclerosis and high cholesterol. Green tea lowers blood cholesterol without side effects and lowers blood pressure using a mechanism employed by modern drugs classified as angiotensin--converting enzyme (ACE) inhibitors. More important, clinical studies have shown that green tea slows the oxidation of low-density lipoprotein (LDL, or "bad") cholesterol into forms that can cause atherosclerotic plaques, although researchers describe this effect as mild. Black tea has a similar effect.
• Breast cancer, endometriosis, fibroeystic breasts, and ovarian, cancer. The polyphenols in green tea occupy many of the sites on the exteriors of cells that otherwise would receive estrogen. This keeps the cells from receiving estrogen, reducing the effects of estrogen on the body. This stops estrogen from stimulating growth of cells in breast, ovarian, and uterine cancer.
• Cancer. A number of animal studies have shown that the polyphenols in
green tea may offer significant protection against cancers of the pancreas,
colon, stomach, lung, and small intestine. It is believed that they do
this by blocking the formation of cancer-causing compounds such as nitroamines,
suppressing the activation of carcinogens, and detoxifying cancer-causing
agents. Other compounds in green tea provide protection from the effects of
repeated exposure to gamma radiation, preventing the development of thyroid
cancer caused by radiation treatment. Green tea catechins prevent the cancer
therapy drug mitomycin (Mutamycin) from causing changes in the bone marrow
that lead to leukopenia, the dangerously low white blood cell counts that
often complicate cancer treatment.
• Cirrhosis of the liver and liver cancer. Researchers have found that, on
average, individuals who consumed large amounts of green tea have lower
levels of certain liver enzymes in their blood, which suggests that green
tea may help prevent liver damage. Up to 30 percent of the weight of a
green tea leaf consists of potent antioxidant catechins. These compounds
help to protect the linings of red blood cells and liver cells from damage
from oxygen free radicals released by toxins and caused by imbalances of
micronutrients in the bloodstream.
• Colorectal cancer and food poisoning. Green tea catechins kill many types
of foodborne bacteria, especially Clostridium bacteria, which are associated
with colon cancer. Laboratory studies with animals have found that the regular
consumption of green tea catechins prevents the growth of colorectal tumors.
• Diabetes. In people with diabetes, green tea extracts suppress the formation
of the "sticky" blood proteins called glycosylation products, which can cause
small blood vessels to thicken and leak. Green tea also keeps sugar out of the
bloodstream in the first place by inhibiting the enzymes in the mouth and
intestines that break down carbohydrates into simple sugars.
• Ear infections, eczema, and periodontal disease. Green tea catechins
prevent Streptococcus mutans from forming dental plaque. (This may explain
why early Asians cleaned their teeth with whisks of green tea leaves-before
the invention of toothpaste.) Green tea's antimicrobial effects make it useful
for other conditions as well, such as ear infections and eczema.
• Herpesvirus infection. Green tea, applied as a compress, increases the
effectiveness of topical interferon treatment of herpes. The green tea
compress is applied first. Then the skin is allowed to dry without washing
before the interferon treatment.
• Influenza. Green tea extract helps ward off the flu by preventing
influenza A viruses from replicating. This effect holds even when the
extract is given at 100 times the concentration of amantadine (Symmetrel),
one of only a few other effective treatments for flu. Green tea extracts
also protect against infection with the influenza B virus, against which
amantadine is not effective and for which zanamivir (Relenza) is only
partially effective.
• Wrinkles. Green tea protects the skin from the effects of harmful free
radicals that can lead to wrinkling.
CONSIDERATIONS FOR USE
Studies suggest that 3 cups (an amount containing the equivalent of 240
to 320 milligrams of polyphenols) of green tea daily provide protection
against cancer. However, other research suggests that as much as 10 cups
per day is necessary to obtain noticeable benefits. Tablets and capsules
containing standardized extracts of polyphenols, particularly EGCG, some
providing 97 percent polyphenol content (equivalent to drinking 4 cups of
tea) are available. Green tea also can be used in cream form or made into
compresses.
Some herbal formulas, particularly those intended for use at the early
stages of cold and flu, act at a molecular level by producing free radicals.
Green tea stops the reactions that form free radicals. You can take green
tea to avoid coming down with colds or flu, but if the flu does strike,
discontinue green tea use until symptoms subside.
You should not take green tea within one hour of taking herbal teas or
patent (over-the-counter) medicines. This avoids diluting the decoction
in the stomach or interfering with the medication. This is especially
important if you are taking codeine, colchicine, or ephedrine, which may
become insoluble in the presence of tannins from green or black tea.
Finally, you should not drink green tea if you are using ginseng regularly.
Green tea can reduce the effectiveness of ginseng. Black tea is not known to
have this effect. If you are pregnant or nursing, you should use only limited
amounts of green tea.
People who are taking monoamine oxidase (MAO) inhibitors or the blood thinner
warfarin (Coumadin) should not use green tea medicinally. Green tea contains
vitamin K, which directly counteracts the blood-thinning action of warfarin.
Certain prescription medications increase the stimulant effects of caffeine
found in green tea. These include the ulcer drug cimetidine (Tagamet) and
antibiotics such as ciprofloxacin (Cipro), enoxacin (Penetrex), and
norfloxacin (Noroxin). Combining green tea (or any other beverage that
contains caffeine) with these medications could result in overstimulation
and insomnia.
from Prescription for Herbal Healing by Phyllis Balch, Copyright ©
January, 2002, Avery Books, a member of Penguin Putnam, Inc., used by
permission.
This is brought to you by Prescription for Herbal Healing.
The most authoritative guide to more than 200 herbs and herbal
preparations.
Phyllis A. Balch, CNC, has been a leading nutritional consultant for
more than two decades, and has spent more than twenty-five years
researching natural approaches to health and healing. She continues
to study nutrition-based therapies, procedures, and treatments in
the United States and abroad.
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