Green Tea

[Spoon]

Camellia sinensis is Latin for the tea plant, the plant species whose leaves and leaf buds are used to produce tea. White tea, green tea, oolong and black tea are all harvested from this species, but are processed differently to attain different levels of oxidation.

It is native to mainland South and Southeast Asia, but is today cultivated across the world, in tropical and subtropical regions.

Camellia sinensis
Principal Proposed Uses
• Cancer Prevention, Gingivitis
Other Proposed Uses
• Diabetes, Heart Disease Prevention, Influenza Prevention, High Cholesterol, Liver Disease Prevention, Rosacea, Sun Damage Protection, Weight Loss

People have been drinking tea for thousands of years, but in the last couple of decades a number of potential health benefits have been attributed to this ancient beverage. Black tea and green tea are made from the same plant, but a higher level of the original substances endure in the less-processed green form.

What Is Green Tea Used for Today?

Green tea contains high levels of substances called catechin polyphenols, known to possess strong antioxidant, anticarcinogenic, antitumorigenic, and even antibiotic properties. Based on these findings, as well as observational studies, green tea has become popular as a daily drink for preventing cancer and heart disease. However, some observational trials failed to find indications of benefit with green tea. Furthermore, only double-blind, placebo-controlled studies can prove a treatment effective, and there is little direct evidence of this type regarding green tea and cancer or heart disease prevention. (For more information on why double-blind studies are so important, see Why Does this Database Rely on Double-blind Studies?) One such study found that green teas produced short term improvements in cholesterol profile, but they disappeared after four weeks. More positive results were seen in a study that evaluated a form of green tea enriched with the substance theaflavin, found in black tea. In this fairly large (over 200 participants) 3-month study, use of the tea product resulted in significant, ongoing reductions in LDL ("bad") cholesterol as compared to placebo. A green tea extract enhanced with catechins has also shown promise for reducing LDL levels, according to one somewhat flawed double-blind study.

Preliminary studies suggest that certain green tea polyphenols may help prevent skin cancer if they are applied directly to the skin. In addition, there is some evidence that green tea constituents might help protect the skin from sun damage. Unlike normal sunscreen preparations, green tea does not physically block ultraviolet light. Rather, it seems to protect cells from some of the damage caused by ultraviolet light. Because it works by such a different mechanism of action, green tea might offer synergistic benefits if combined with standard sunscreens. However, in an 8-week double-blind, placebo-controlled study of forty women who already had symptoms of aging skin, combined use of oral green tea and a topical green tea cream failed to prove more effective than placebo. Some possible benefits were seen in microscopic evaluation of skin condition.

Topical green tea extracts have also shown a bit of promise for the treatment of cervical dysplasia, while oral green tea extracts might reduce risk of prostate cancer, according to a small pilot study.

On a completely different note, one interesting study tested the effectiveness of gargling with green tea catechins as a means of preventing influenza. In this double-blind, placebo-controlled study, 124 residents of a Japanese nursing home gargled with green tea catechins or placebo for three months. All participants received standard influenze vaccine. The results showed that residents who gargled with the tea extract were less likely to develop influenza than those using the placebo.

A small double-blind, placebo-controlled trial found weak evidence that green tea chew candy might reduce gum inflammation in individuals with periodontal disease (gingivitis).

Oral use of green tea extracts has shown a bit of promise for treating borderline diabetes.

Green tea has been proposed as means of preventing liver disease, but the evidence for this use remains unconvincing.

Green tea is sometimes recommended for weight loss on the basis of rather theoretical evidence that it speeds up metabolism. However, there is little direct scientific backing for this use. Other evidence indicates that if green tea increases metabolism at all, the effect is extremely small. However, a controlled study failed to find green tea helpful for preventing weight regain after weight loss. Green tea extract enriched with catechins has done better, enhancing weight loss in one substantial but somewhat flawed trial. Oolong tea enriched with green tea extracts has also shown promise. However, use of green tea failed to produce significant weight loss in a study of overweight women with polycystic ovary syndrome.

One preliminary study, available only in abstract form, found some evidence that green tea cream may be helpful for rosacea . The results of another study weakly hint that green tea extracts taken orally might reduce symptoms of benign prostatic hyperplasia.

One study found that inhaled tea catechins could reduce levels of resistant staph carried in the sputum of disabled seniors. . NOTE: Do not attempt to inhale green tea products.

Studies weakly suggest that 3 cups of green tea daily might provide protection against cancer. However, because not everyone wants to take the time to drink green tea, manufacturers have offered extracts that can be taken in pill form. A typical dosage is 100 to 150 mg three times daily of a green tea extract standardized to contain 80% total polyphenols and 50% epigallocatechin gallate. Whether these extracts offer any benefit remains unknown. Furthermore, there are growing concerns about liver toxicity with use of green tea extracts. (see Safety Issues)

Warning: In an analysis performed in 2006 by the respected testing organization ConsumerLabs.com, some tested green tea products were found to be contaminated with lead.

Safety Issues

As a widely consumed beverage, green tea is generally regarded as safe. It does contain caffeine, at perhaps a slightly lower level than black tea, and can therefore cause insomnia, nervousness, and the other well-known symptoms of excess caffeine intake.

Green tea extracts, however, may not be safe. There are a growing number of case reports in which use of a concentrated green tea extract was associated with liver inflammation; in most cases, liver problems disappeared after the extract was discontinued, but in two cases, permanent liver failure ensued requiring liver transplantation. While it is not absolutely certain that the green tea extract caused the liver problems, nor how it might do so, these reports do raise significant concerns about use of green tea extracts, especially by those with liver disease or prone to it.

Green tea should not be given to infants and young children. There are theoretical concerns that high dosages of EGCG might be unsafe for pregnant women.

Dried green tea leaf contains significant levels of vitamin K on a per-weight basis. On this basis, it has been stated that people using blood thinners in the Coumadin family should avoid green tea, because vitamin K antagonizes the effect of those drugs. However green tea taken as a beverage provides such small amounts of the vitamin that the risk seems minimal for normal consumption. There is one case report of problems that developed in a person on warfarin who consumed as much as a gallon of green tea daily.

Interactions You Should Know About

If you are taking

* MAO inhibitors : The caffeine in green tea could cause serious problems.
* Coumadin (warfarin) : avoid drinking large quantities of green tea.


I have, personally, been taking green tea supplements for quite a while now, and also like to drink it - hot with a lemon wedge is my favorite, I think. I am hoping that the info about green tea extracts not being safe is not true...is it good for you or not? It seems that what they say is good for you changes every day! What do you have to say? What do you know, think, or want to add about GREEN TEA? Add your comments by replying to this thread. We would love to hear what you have to add!

[samson]

Green tea is cool.
Love it.
There are white tea, another kind of healthly tea.