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The Miracle of Green Tea
"Better to be deprived of food for three days, than tea for one." (Ancient Chinese Proverb)
Is any other food or drink reported to have as many health benefits as green tea? The Chinese have known about the medicinal benefits of green tea since ancient times, using it to treat everything from headaches to depression. In her book Green Tea: The Natural Secret for a Healthier Life, Nadine Taylor states that green tea has been used as a medicine in China for at least 4,000 years.
Today, scientific research in both Asia and the west is providing hard evidence for the health benefits long associated with drinking green tea. For example, in 1994 the Journal of the National Cancer Institute published the results of an epidemiological study indicating that drinking green tea reduced the risk of esophageal cancer in Chinese men and women by nearly sixty percent. University of Purdue researchers recently concluded that a compound in green tea inhibits the growth of cancer cells. There is also research indicating that drinking green tea lowers total cholesterol levels, as well as improving the ratio of good (HDL) cholesterol to bad (LDL) cholesterol.
To sum up, here are just a few medical conditions in which drinking green tea is reputed to be helpful:
cancer
rheumatoid arthritis
high cholesterol levels
cariovascular disease
infection
impaired immune function
What makes green tea so special?
The secret of green tea lies in the fact it is rich in catechin polyphenols, particularly epigallocatechin gallate (EGCG). EGCG is a powerful anti-oxidant: besides inhibiting the growth of cancer cells, it kills cancer cells without harming healthy tissue. It has also been effective in lowering LDL cholesterol levels, and inhibiting the abnormal formation of blood clots. The latter takes on added importance when you consider that thrombosis (the formation of abnormal blood clots) is the leading cause of heart attacks and stroke.
Links are being made between the effects of drinking green tea and the "French Paradox." For years, researchers were puzzled by the fact that, despite consuming a diet rich in fat, the French have a lower incidence of heart disease than Americans. The answer was found to lie in red wine, which contains resveratrol, a polyphenol that limits the negative effects of smoking and a fatty diet. In a 1997 study, researchers from the University of Kansas determined that EGCG is twice as powerful as resveratrol, which may explain why the rate of heart disease among Japanese men is quite low, even though approximately seventy-five percent are smokers.
Why don't other Chinese teas have similar health-giving properties? Green, oolong, and black teas all come from the leaves of the Camellia sinensis plant. What sets green tea apart is the way it is processed. Green tea leaves are steamed, which prevents the EGCG compound from being oxidized. By contrast, black and oolong tea leaves are made from fermented leaves, which results in the EGCG being converted into other compounds that are not nearly as effective in preventing and fighting various diseases.
Other Benefits
New evidence is emerging that green tea can even help dieters. In November, 1999, the American Journal of Clinical Nutrition published the results of a study at the University of Geneva in Switzerland. Researchers found that men who were given a combination of caffeine and green tea extract burned more calories than those given only caffeine or a placebo.
Green tea can even help prevent tooth decay! Just as its bacteria-destroying abilities can help prevent food poisoning, it can also kill the bacteria that causes dental plaque. Meanwhile, skin preparations containing green tea - from deodorants to creams - are starting to appear on the market.
Harmful Effects?
To date, the only negative side effect reported from drinking green tea is insomnia due to the fact that it contains caffeine. However, green tea contains less caffeine than coffee: there are approximately thirty to sixty mg. of caffeine in six - eight ounces of tea, compared to over one-hundred mg. in eight ounces of coffee.
There are as many answers to this question as there are researchers investigating the natural properties of green tea. For example, Herbs for Health magazine cites a Japanese report stating that men who drank ten cups of green tea per day stayed cancer-free for three years longer than men who drank less than three cups a day (there are approximately 240 - 320 mg of polyphenols in three cups of green tea). Meanwhile, a study by Cleveland's Western Reserve University concluded that drinking four or more cups of green tea per day could help prevent rheumatoid arthritis, or reduce symptoms in individuals already suffering from the disease. And Japanese scientists at the Saitama Cancer Research Institute discovered that there were fewer recurrances of breast cancer, and the disease spread less quickly, in women with a history of drinking five cups or more of green tea daily.
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It gets more confusing. A University of California study on the cancer-preventative qualities of green tea concluded that you could probably attain the desired level of polyphenols by drinking merely two cups per day. On the other hand, a company selling a green tea capsule formula insists that ten cups per day are necessary to reap the maximum benefits.
How can you make sense of these conflicting claims? Given all the evidence, it is probably safe to plan on drinking four to five cups of green tea per daily. If you're a real devotee, by all means drink more; but whether or not you'll derive added health benefits remains to be determined by further research.
Caffeine
Unless specifically decaffeinated, green tea contains caffeine. Normal green tea itself may contain more caffeine than coffee (by dry weight--for caffeine per serving size, see below), but the length of infusion with hot water and the number of times the leaves are reused can greatly alter caffeine intake. Using a given amount of green tea leaves steeped in 100 mL of water, experiments have shown that after the first 5 minutes of brewing, the tea contains 32 mg caffeine. But if the same leaves are then used for a second and then a third five minute brew, the caffeine drops to 12 mg and then 4 mg, respectively.
While coffee and tea are both sources of caffeine, the amounts of caffeine in any single serving of these beverages varies significantly. An average serving of coffee contains the most caffeine, the same serving size of tea provides 1/2 to 1/3 as much. One of the more confusing aspects of caffeine content is the fact that coffee contains less caffeine than tea when measured in its dry form. The caffeine content of a prepared cup of coffee is significantly higher than the caffeine content of a prepared cup of tea.
Green teas contain two caffeine metabolites (caffeine-like substances): theophylline, which is a stronger stimulant than caffeine, and theobromine, which is slightly weaker than caffeine.
How to Brew a Cup of Green Tea
Producing the perfect cup of green tea is a tricky process. If not handled properly, those same polyphenols that provide health benefits can ruin the flavor, making the tea taste "gassy." It's particularly important not to overbrew. While it's best to follow the manufacturer's instructions for each variety of green tea, here are some general instructions:
Use one tea bag, or 2 - 4 grams of tea,* per cup.
Fill a kettle with cold water and bring to a boil.
After unplugging the kettle, allow it to stand for up to 3 minutes.
Pour the heated water over the tea bag or tea, and allow it to steep for up to 3 minutes. If using a tea bag, remove the bag.
Allow the tea to cool for three more minutes.
*One to two teaspoons, depending on the variety of green tea you are brewing.
Does it Inhibit HIV?
For many years, green tea has been associated with positive health benefits. In a recent study by researchers at Purdue University, the nature of these benefits was identified. The researchers found that epigallocatechin gallate (EGCg), a compound found in the tea, inhibited the growth of cancer cells. A study from the University of Tokyo has shown that EGCg binds to CD4 cells, prventing HIV from binding to and destroying the cell in the process. Experts feel that the substances found in green tea, specifically EGCg, could lead to the devlopment of new HIV medications.
How Much Green Tea Do We Need?
Green tea leaves are potent in EGCg. The study suggests that consumption of four to five cups of green tea may slow cancer. However, the studies of green tea and it's binding to CD4 used concentrations many times higher than those that could be acheived by drinking green tea. However, understanding the mechanism by which EGCg binds to the CD4 cell could point scientists in new directions when researching new drugs and treatment targets.
Do Other Types of Tea Have the Same Benefits?
All tea comes from the same botanical source. Compared to other types of tea, green tea is processed differently. In green tea, the leaves are not allowed to oxidize but instead are steamed. This process allows the natural ingredients in the leaves to be preserved. Other types of tea were not nearly as successful as green tea in inhibiting the cancerous cells or HIV. In the end, green tea was approximately ten times more potent than the other types.
The scientists want to expand on these studies and determine the exact mechanism of EGCg. At this point, the scientists are beginning to understand the initial inhibitive effects of EGCg but further research is warranted to pin down the exact mechanisms and to put that mechanism to work fighting HIV.
Green Tea for Weight Loss?
Background:Current interest in the role of functional foods in weight control has focused on plant ingredients capable of interfering with the sympathoadrenal system.
Objective: We investigated whether a green tea extract, by virtue of its high content of caffeine and catechin polyphenols, could increase 24-h energy expenditure (EE) and fat oxidation in humans.
Design: Twenty-four–hour EE, the respiratory quotient (RQ), and the urinary excretion of nitrogen and catecholamines were measured in a respiratory chamber in 10 healthy men. On 3 separate occasions, subjects were randomly assigned among 3 treatments: green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), and placebo, which they ingested at breakfast, lunch, and dinner.
Results: Relative to placebo, treatment with the green tea extract resulted in a significant increase in 24-h EE (4%; P < 0.01) and a significant decrease in 24-h RQ (from 0.88 to 0.85; P < 0.001) without any change in urinary nitrogen. Twenty-four–hour urinary norepinephrine excretion was higher during treatment with the green tea extract than with the placebo (40%, P < 0.05). Treatment with caffeine in amounts equivalent to those found in the green tea extract had no effect on EE and RQ nor on urinary nitrogen or catecholamines.
Conclusions: Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content per se. The green tea extract may play a role in the control of body composition via sympathetic activation of thermogenesis, fat oxidation, or both.
Key Words: Obesity • thermogenesis • catechins • polyphenols • caffeine • sympathetic nervous system • green tea • fat oxidation • catecholamines • men
Hidden Benefits of Green Tea
Considered by many to be one of nature's healthiest beverages, green tea is rich in antioxidants that could help fight off heart disease and cancer. Made from unfermented leaves of the Camellia sinensis plant, green tea is also low in caffeine (offering about 8 to 30 mg per cup, compared to 100 to 350 mg per cup of coffee) and contains the amino acid L-theanine (shown to induce relaxation and relieve stress in preliminary research).
Now, a number of studies are exploring the benefits beyond green tea's heart-healthy, anti-cancer, stress-reducing effects. Here's a look at some of the most promising findings so far.
1) Healthy Teeth and Gums
In a 2009 study, scientists sized up the periodontal health of 940 men and found that those who drank green tea on a regular basis had healthier gums than participants who skimped on the drink. For every cup of green tea sipped daily, in fact, there was a significant decrease in several indicators of periodontal disease (such as bleeding upon probing of the gum tissue).
Past research also indicates that drinking green tea may help you avoid tooth erosion.
2) Stroke Prevention
Another 2009 study suggests that drinking green tea each day can significantly slash your risk of stroke (the third leading cause of death in the United States). In reviewing nine studies on a total of nearly 195,000 people, researchers found that three daily cups of tea reduced stroke risk by 21%. What's more, consuming three more cups a day appeared to decrease stroke risk by an additional 21%.
3) Better Brain Power
Gulping green tea could preserve your brain power as you age, according to a 2006 study. The study's authors looked at tea consumption among 1,003 Japanese people (ages 70 and up), finding that those who drank the most green tea were the least likely to show signs of weakened brain function. For instance, study members who had a cup of green tea four to six times weekly were 38% less likely to display signs of cognitive impairment than those who drank green tea less than three times per week.
Traditional Chinese Tea Brewing Method (with pictures!)
http://chinesefood.about.com/gi/dynamic ... method.htm
What the Science Says
Laboratory studies suggest that green tea may help protect against or slow the growth of certain cancers, but studies in people have shown mixed results.
Some evidence suggests that the use of green tea preparations improves mental alertness, most likely because of its caffeine content. There are not enough reliable data to determine whether green tea can aid in weight loss, lower blood cholesterol levels, or protect the skin from sun damage.
NCCAM is supporting studies to learn more about the components in green tea and their effects on conditions such as cancer, diabetes, and heart disease.
Side Effects and Cautions
Green tea is safe for most adults when used in moderate amounts.
There have been some case reports of liver problems in people taking concentrated green tea extracts. This problem does not seem to be connected with green tea infusions or beverages. Although these cases are very rare and the evidence is not definitive, experts suggest that concentrated green tea extracts be taken with food, and that people should discontinue use and consult a heath care practitioner if they have a liver disorder or develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice.
Green tea and green tea extracts contain caffeine. Caffeine can cause insomnia, anxiety, irritability, upset stomach, nausea, diarrhea, or frequent urination in some people.
Green tea contains small amounts of vitamin K, which can make anticoagulant drugs, such as warfarin, less effective.
Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.