he prefecture of Shizuoka, Japan has two claims to fame. First, it is the heart of this tea-drinking country's tea region. Not only do the inhabitants grow and process huge amounts of tea here, they also produce - and consume - large amounts of tea-containing products, including tea-flavored gum, candy, toothpaste, and even shampoo, not to mention drink multiple cups of tea every day.

Shizuoka is also becoming well known because of its extraordinarily low death rate from cancer, especially stomach cancer. When Japanese researchers looked more closely at the demographics of the region, they found that those towns with the highest tea consumption had the lowest levels of cancer.¹

Coincidence? Not likely. Recent scientific studies are confirming at least 4000 years of folklore and medical practice in Asia regarding the incredible health benefits of green tea. Tea, and especially green tea, which is second only to water as the most common drink in the world, may also be the single most valuable substance you can take to protect your general health. The many health benefits of tea, all of which have been demonstrated in scientific studies, include:

• Antioxidant activity
• Cancer protection
• Cholesterol reduction
• Blood pressure reduction
• Antibacterial and antiviral activity
• Protection against radiation
• Reduction of body fat
• Reduction of blood sugar

Tea Polyphenols
The key fraction of the tea leaf (Camellia sinensis) that provides all these health benefits is a group of phytochemicals known as polyphenols. Long known as tea tannin because of their pungent taste, polyphenols constitute 15 to 30% of unfermented dried green tea and most of the soluble portion of tea. Thus, when you drink a cup of green tea, you're basically drinking a solution of tea polyphenols. In fresh, unfermented tea leaves, polyphenols exist as a series of chemicals called catechins, which include gallocatechin (GC), epigallocatechin (EGC), epicatechin (EC), epigallocatechin gallate (EGCg), and epicatechin gallate (ECg). As you can see in Figure 1, the largest component of fresh tea leaves is EGCg, which is fortunate, because it is also the most potent.Our focus so far has been on green tea, but we Westerners are most familiar with black tea, which has significantly fewer polyphenols, and thus appears to be generally less beneficial. Both black and green tea come from the same source, but the leaves that eventually become black tea are first broken up and exposed to air. This process promotes oxidation and deactivation of the valuable polyphenols. Green tea, on the other hand, is processed in a way that protects polyphenols by destroying the enzyme that oxidizes them. Consequently, green tea may contain as much as 90% more polyphenols than black tea. Before you run down to your local market to pick up some green tea, consider first that the amount of protection you get from green tea is directly proportional to how much of it you drink² (Fig.2).

Sipping a cup at breakfast might help a little, but to reap the full protective rewards of green tea, you need to drink at least 5 to 10 cups a day. This level of tea consumption is not uncommon in Asia, but for most Americans it probably represents a significant shift. But take heart, drinking tea is not the only way to obtain its health benefits. Once it was discovered that tea catechins play such an important protective role, Japanese scientists went to work to isolate these key ingredients and translate them into a form that would (1) concentrate the nutrients in a smaller package and (2) put them in a vehicle that would be more accessible to non-tea drinkers. The result of these efforts is Life Enhancement's Green Tea Extract. Each Green Tea Extract capsule contains 40% polyphenols, including about 10% EGCg, the most biologically active and impressive of the polyphenols.

The clinical benefits of green tea are truly extraordinary. The following is a brief overview of some of the most important studies of the effects of tea on various disease states.

Cancer Protection
In addition to the observations of the people of Shizuoka, it is well known that Japanese men get less lung cancer than American men even though they smoke more cigarettes. It is thought that this difference may be due to their consumption of green tea. One study compared the frequency of a particular marker of lung cancer, the degradation of lymphocytes, in smokers and nonsmokers. Known as SCE (sister chromatid exchange in mitogen-stimulated peripheral lymphocytes), this marker was found to be significantly elevated in smokers who did not drink green tea whereas, in those who drank green tea, the SCE frequency was comparable to that of nonsmokers.³

When mice were exposed to the carcinogens in cigarette smoke, those fed green tea extract had 45% lower incidence of lung cancer than their control counterparts.⁴ Scores of similar studies have also demonstrated protection against cancers of the esophagus, stomach, skin, breast, pancreas, colon/rectum, and liver in vitro, in tea-drinking humans, and in animals fed green tea.^5-10 Green tea has been found to be effective even against established skin cancers in mice.^11,12

Exactly how green tea fights cancer is currently under investigation in laboratories all over the world. Current theories are focusing on the antioxidant and antiproliferative effects of polyphenolic compounds. It is also thought that these polyphenols may inhibit carcinogenesis by blocking the endogenous formation of N-nitroso compounds, suppressing the activation of carcinogens, and trapping genotoxic agents.¹³ It may be possible that EGCg and other tea catechins block the interaction of tumor promoters with their receptors. This phenomenon has been described as having a kind of "sealing" effect, because these factors are neutralized by sealing them off from the receptors.¹⁴

Superior Antioxidant Activity

Fig. 3. Anioxidative activity of tea catechins, vitamin E, and BHA on salad oil.

The antioxidant fraction of green tea extract has been shown to efficiently scavenge pro-oxidants such as hydrogen peroxide, the superoxide anion radical,¹⁵ and the ascorbyl radical.¹⁶ In a study comparing the antioxidant effects of green tea and black tea, green tea was found to be six times more potent. Curiously, this antioxidant activity may be attenuated by drinking tea with milk, possibly because the milk proteins neutralize the tea polyphenols.¹⁷ Green tea's antioxidant activity is particularly important for preventing lipid peroxidation, a crucial step in the formation of atherosclerotic plaque. Since lipid peroxidation is also a factor in the spoilage of oils and fatty constituents of many foods, antioxidants, including polyphenols and vitamin E, are often added to prevent rancidity. When two different concentrations of tea catechins were compared with two other powerful antioxidants, vitamin E and butylated hydroxyanisole (BHA), for their ability to protect fats and oils from oxidation, tea catechins were clearly superior (Fig. 3). The tea catechins were also able to suppress the photo-oxidation of certain oils, and showed marked synergistic effects with tocopherols (vitamin E), ascorbic acid (vitamin C) and some organic acids.

Heart Disease Protection
Green Tea Extract provides protection against cardiovascular diseases by a variety of actions, including reducing platelet aggregation, lowering cholesterol, and decreasing blood pressure.

Antiplatelet activity. Platelets, which are cell fragments critical to the blood clotting process, have a tendency to clump together, or aggregate. When this occurs at the site of a wound forming a plug (or blood clot), it can be life-saving, but when it occurs inside blood vessels, it can lead to reduced blood flow, impaired oxygen delivery to certain tissue regions, and, ultimately, cellular death. Blood clots that prevent the normal flow of blood to the heart (heart attack/myocardial infarction) or brain (stroke) can be fatal.

Evidence suggests that Green Tea Extract possesses pronounced antiplatelet activity. EGCg, the most potent anti-clotting component of green tea, has antiplatelet activity comparable to that of aspirin. Unlike aspirin, though, EGCg does not irritate the stomach, and, also unlike aspirin, it blocks the platelet aggregation caused by Platelet Activating Factor (PAF), an action typically associated with extracts of Ginkgo biloba.^18,19

Cholesterol reducing activity. Feeding studies in animals have revealed a significant hypolipidemic action of Green Tea Extract. In one study, rats were fed a lard-enriched diet for 28 days; the diet of some of the animals was also supplemented with Green Tea Extract. Those rats fed the tea extract showed significant reductions in plasma total cholesterol, VLDL- and LDL- (the "bad") cholesterol, and relative increases in HDL (the "good") cholesterol.^20,21

In one experiment, rats were fed a high-fat, high-cholesterol diet. After 4 weeks, the total cholesterol concentration in the group that did not receive EGCg rose to more than twice the level of the control (normal diet) group. In particular, the LDL-cholesterol level increased by as much as 15-fold and the HDL-cholesterol level dropped by more than half. The addition of 0.5% EGCg to the diet suppressed the LDL-cholesterol increase to less than 8-fold and the decrease in HDL-cholesterol was completely inhibited. In those rats fed a diet containing 1.0% EGCg, this effect was even more pronounced. These results suggest that dietary hyperlipidemia can be controlled to a large degree simply by ingesting a green tea extract containing EGCg.

A similar beneficial effect seems to occur in humans. In one study of more than 2000 Japanese men aged 49-55, tea consumption (10 cups/day) was found to be significantly inversely associated with serum levels of total cholesterol and LDL-cholesterol, but not with HDL-cholesterol or triglycerides.²² Another study in a different population of more than 1300 Japanese males yielded a similar result.²³

Antihypertensive Effect
In hypertension caused by high blood pressure, angiotensin I converting enzyme (ACE) converts angiotensin I to vasoconstrictive angiotensin II. By blocking this conversion, it is possible to prevent hypertension to a large degree. This is the mechanism that drugs known as ACE inhibitors exploit to treat this disease. But ACE-inhibiting drugs are not the only way to go.

It turns out that green tea polyphenols also have significant ACE-inhibiting ability. In one study, tea polyphenols were given to one group of genetically hypertensive rats beginning 1 week after weaning; a second group received a normal diet. After 16 weeks, the diets were switched. The blood pressure in the normal diet group already exceeded 200 mm Hg at age 10 weeks, compared with no clear rise in blood pressure in the tea polyphenol-treated group. When the diets of both groups were switched at 16 weeks, the blood pressure soon changed accordingly. In addition, the researchers found that the hypertensive rats on a normal diet were significantly more likely to die of a stroke.

Antibacterial and Antiviral Activity
Green tea has long been a folk remedy for treating diarrhea. Recent research has now revealed the reason. Tea catechins are powerful antibacterial and antiviral agents which makes them effective for treating everything from tooth decay to HIV. Studies have demonstrated that tea catechins can protect mice against infection by the bacteria that cause cholera and inhibit the activity of cholera toxin;²⁴ inhibit the growth of Clostridium spp, which contributes to a variety of human diseases resulting in sudden death, toxicity, mutagenesis, carcinogenesis, and aging;²⁵ and kill methicillin-resistant Staphylococcus aureus in the respiratory tract and also make these bacteria more susceptible to oxacillin.²⁶

No less startling is the effect of green tea extract on viral infections. Japanese researchers have now demonstrated that EGCg and other tea polyphenols prevent the influenza virus from attaching itself to normal cells, thus blocking its infectivity. Even a small amount of EGCg seems to be capable of placing a significant obstacle in the way of the flu virus.²⁷ Evidence also suggests activity against infections caused by rotavirus and enterovirus, which are common causes of diarrhea.²⁸ Perhaps the best-documented antimicrobial effect of tea catechins is against the bacteria that cause tooth decay, Streptococcus mutans. In fact, green tea is probably better than fluoride for keeping teeth healthy.²⁹ In one study, green tea was found to be far more effective than other forms of tea against S mutans (See Fig. 4). Another recent study found that EGCg completely inhibited the growth and cellular adherence of another important oral bacteria, Porphyromonas gingivalis.³⁰ It has even been suggested that green tea be used as prophylactic treatment in root canal because of its broad spectrum of antibacterial and bactericidal activity.³¹

Using Green Tea Extract

Fig. 4. Antibacterial effect of tea against carcinogenic bacteria (S mutans)

So for those who want all of these health benefits but are daunted by the prospect of fitting 5 to 10 cups of tea into their daily routine, Green Tea Extract solves the problem by supplying the key tea polyphenols in a highly concentrated formulation.

Each 500-mg capsule of Green Tea Extract contains at least 40% highly purified polyphenols, including EGCg, equivalent to as much as 10 cups of green tea. Excessive caffeine is not a significant problem, because Green Tea Extract contains only a fraction of what is found in coffee. Considering the wide safety margin of Green Tea Extract and the fact that benefits have been documented at over 10 cups of tea per day, we recommend taking 1 to 5 capsules spread out throughout the day.

If you're concerned about protecting yourself from the bacteria that cause tooth decay, it is necessary to drink tea without milk. To do this, simply open a capsule of Green Tea Extract into a cup of hot water and let it steep, the way you would with any loose tea. Then drink up, being sure to swish the liquid around in your mouth so that it contacts all surfaces.

Extravagant claims are often associated with novel nutritional supplements and botanicals, but how many possess a history as rich as that of green tea, or have been exposed to as much scientific scrutiny? Perhaps the ancient Chinese medical book from the Tang Dynasty, Lost Property of Medical Herbs, was correct when it stated,

References

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