Green Tea and Thermogenesis

Green Tea and Thermogenesis
The color (green, oolong, and black) of tea (Camellia sinensis) is determined by how it is manufactured. Green tea is prepared in such a way as to avoid the oxidation of the polyphenols; oolong tea is partially oxidized; black tea is largely oxidized.

The composition of tea is determined by soil conditions, the season the leaves are harvested, and the method used to process the tea. As a rough guide, green tea contains 2.9 to 4.2% caffeine, 0.02 to 0.04% theophylline, and 0.15 to 0.2% theobromine. Green tea also contains theanine, an important water-soluble amino acid that is converted to catechin by sun light. The greatest theanine content is found in the highest grade green tea, Gyokuro, which is cultivated without direct sunlight.

Green tea also contains a number of polyphenolic compounds. The catechin epigallocatechin gallate (EGCG) is the most abundant (> 50% of total tea catechins). It is also believed to be the most pharmacologically active. The other main catechins are epicatechin (EC), epicatechin gallate (ECG), and epigallocatechin (EGC). You can view the chemical structures in a new window.

In addition to stimulating thermogenesis, green tea has a variety of well documented health benefits. Green tea is an antioxidant that has a strong anticancer effects in skin, stomach, colon, etc. Green tea protects against free radicals and it is a logical addition to any supplement program designed to prevent heart disease. In fact, green tea has so many health benefits that this post will have to focus on its ability to stimulate thermogenesis.

Quick facts: The Dulloo et al. studies (1, 2) used an alcohol extract of green tea that is sold in capsule form under the name EXOLISE (Arkopharma Laboratories, Nice, France). This extract is standardized to 24.7% catechins (70% as EGCG), and 8.35% caffeine.
How Powerful Is Green Tea Thermogenesis?
Scientists have found that green tea stimulates thermogenesis and this effect cannot be completely attributed to its caffeine content because the thermogenic effect of green tea is greater than an equivalent amount of caffeine. An in vitro study by Dulloo et al (2) found that a catechin that is abundant in green tea, EGCG, increased the respiration rate of brown fat (stimulated thermogenesis). Dulloo et al. have also done an in vivo study (1) that involved "10 healthy men" who received (with each meal during a 24 hour test period) on three separate occasions:

Test 1: 50 mg caffeine and 90 mg EGCG (total catechins: 125 mg).

Test 2: 50 mg caffeine.

Test 3: Placebo.

There was a "5-10 day interval between successive 24-h trials for each subject." The conditions were controlled and the study was double blind. However, given the fact that obese people respond differently to sympathetic stimuli, it is unfortunate that these tests were performed on "healthy" subjects. The study accepted people described as ranging from "lean to mildly obese" (8-30% bodyfat). But the responses varied widely nonetheless: 24 hour energy expenditure increased "in 6 of the 10 subjects after treatment with the green tea extract, ranging from 266 to 836 kJ" They did not find a correlation between the magnitude of thermogenic response and the degree of fatness of the subjects. That's not too surprising given the number of subjects and the selection criteria. It's a shame that they didn't include more subjects and some fat people in these tests.


Energy Expenditure
Diurnal and 24 hour energy expenditure was increased significantly during treatment with green tea extract. Nocturnal energy expenditure increased, but not significantly. Here's the numbers:

Diurnal: Green tea 4.5% > placebo; Green tea 3.2% > caffeine.
24 hour: Green tea 3.5 % > placebo; Green tea 2.8 % > caffeine.
Perhaps even more interesting is the fact that the green tea extract produced lower respiratory quotients (helped normalize FAT burning):

"Significant differences across treatments were found during the diurnal, nocturnal, and 24-h periods . . . The contribution of fat oxidation [fat burning] to 24-h EE [energy expenditure] during treatment with the green tea extract (41.5%) was significantly higher (p<0.001) than during placebo [31.6%] treatment" (1).

In addition, urinary nitrogen losses showed no significant differences across treatments during all three periods. Clearly, the increased energy expenditure reflects increased FAT burning. This is worth exploring in greater detail.

Written
Dec 2000
Last Update
Dec 2000
Respiratory Quotient
Now we are getting to the interesting stuff. The lower the respiratory quotient, the more fat you are burning. You will often see this referred to as substrate utilization, substrate oxidation (burning), or fuel mix. It is very encouraging that such a small dose of green tea had such an impressive effect on the RQ: The contribution of fat oxidation [fat burning] to 24-h EE [energy expenditure] during treatment with the green tea extract (41.5%) was significantly higher (p<0.001) than during placebo [31.6%] treatment" [emphasis added] (1). Outside of medical journals, fat oxidation and the respiratory quotient are usually only discussed in relation to aerobic exercise (I'm sure you have been told to do low intensity aerobics to burn more fat). However, as usual, the interesting stuff (the stuff that proves obesity is a REAL disease) is ignored.

You see, obese people tend to burn more carbohydrate (glucose) and less fat (fatty acids) than normal people. The Astrup/Toubro team of obesity researchers have studied this defect (4-NA, 5-NA). In fact, a growing number of scientists believe that this part of the thermogenic defect may be more important than energy expenditure. Why do we burn relatively less fat? This is caused be a number of genetic (22) and biochemical defects including insufficient release of noradrenaline and adrenaline. Arne Astrup et al. (5-NA, 22) have written about this genetic defect:

"Direct evidence for a genetic influence on RQ [respiratory quotient] was delivered by Deriaz et al., who studied the relationship between DNA variation at the genes coding for the Na,K-ATPase peptides, RQ, and body fat. Postabsorptive [after a meal] RQ was found to be associated with the alpha2-gene and linked with the beta-gene of the Na,K-ATPase, which suggests that these, or neighboring genes, influence RQ. Twin studies also support the heritability of RQ." [emphasis added] (5-NA).

Based on this study by Dulloo et al. (1), it looks like green tea can help correct this respiratory quotient defect. Of course, ephedrine/caffeine normalizes the release of noradrenaline and adrenaline and corrects the respiratory quotient:

"The respiratory quotient (RQ) indicate that relatively more lipid [fat] was oxidized during chronic ephedrine treatment than in the control study. This change was observed in the fasting state as well as after glucose administration. Certain effects of ephedrine seems to be appropriate to a thermogenic drug for the treatment of obesity: A single dose of ephedrine stimulates thermogenesis, an effect that is enhanced during chronic treatment; Chronic treatment elevates the metabolic rate; and the substrate utilization is changed in favor of lipid [fat] oxidation" [emphasis added] (6).

Is it not curious that doctors tell obese people to eat an abnormally small amount of fat rather than tell us to take thermogenic supplements to correct this genetic fat burning defect? I mean, imagine if your car was having engine trouble and your mechanic refused to fix it and told you to "just drive less." Of course, you would immediately realize that this was a bogus 'solution' and go to another mechanic. But what if they ALL ignored the problem and told you to change your driving habits? Eventually you would realize that you need to read some repair manuals so you can fix the car yourself, right? Fortunately, there is no FDA-type organization trying to pass laws against nonprofessional car repairs.

Obese people who do not want to be mislead by prejudice, ignorance, or political/financial agendas should keep this fuel mix defect in mind when they hear "experts" questioning the importance of thermogenesis. Typically, these "experts" will rattle off a bunch of energy expenditure numbers and tell you that thermogenesis is not very important and thermogenic supplements don't do much. If you want to have some fun, remind the "expert" that there is direct evidence for a genetic influence on respiratory quotient and one of the ways that thermogenic supplements help obese people is by normalizing their defective substrate utilization. Ask the "expert" if he is aware of the fact that a growing number of obesity scientists believe correcting this genetic fat burning defect is more important than those archaic energy expenditure numbers. After all, if you don't BURN fat, you BECOME fat.


Noradrenaline Storage & Release
In order to understand how green tea works we need to take a quick look at noradrenaline storage, release, and metabolism. Noradrenaline is synthesized in the sympathetic nerves and stored in storage vesicles. When sufficiently stimulated, the vesicles migrate to the end of the nerve and release noradrenaline into the synaptic cleft. As you probably already know, the noradrenaline binds to the adrenergic receptors and stimulates thermogenesis. Next in the chain of events is noradrenaline metabolism, which involves two uptake mechanisms.

General references for Noradrenaline Storage, Release, and Metabolism: 3-BK, 20-BK, 21-BK.

Advanced readers should check out "Principles of Neuropsychopharmacology" (3-BK) -- it's an excellent book!






Noradrenaline Metabolism
Uptake 1: After stimulating the adrenergic receptors, 85-90% of the noradrenaline is taken back up into the sympathetic nerves (uptake 1) and stored in vesicles or metabolized by monoamine oxidase (specifically, MAO-A) in the mitochondria. The importance of uptake 1 (neuronal uptake) is reflected by the warnings against combining sympathomimetics (ephedrine, phentermine, etc.) that increase noradrenaline release with MAO inhibitors -- the risk of overstimulation would be much too high.

Uptake 2: Some of the noradrenaline diffuses away from the receptors and is transported by extra-neuronal cells (uptake 2) and metabolized by catechol-O-methyl-transferase (COMT). Green tea increases noradrenaline in the synaptic cleft and safely increases thermogenesis because of its ability to prevent COMT from metabolizing noradrenaline. This is safe because COMT plays a much smaller role in catecholamine dynamics than MAO.

COMT exists in both a soluble and a membrane-bound form. The soluble form of COMT is found in organs and it does not have as high of an affinity for catecholamines as the membrane-bound form.

Quick facts: Uptake 1 of noradrenaline is blocked by cocaine, amphetamines, and tricyclic antidepressants. Progesterone increases MAO and estrogen inhibits MAO.


* There is more information on how caffeine enhances thermogenesis in the following posts: How ECA Works has illustrations and there is referenced information in The "A" in ECA and my Thermogenic FAQ.
How Green Tea Stimulates Thermogenesis
The thermogenic effect of green tea involves two mechanisms: I.) green tea contains a catechin, EGCG, which inhibits catechol O-methyltransferase (COMT), an enzyme that degrades noradrenaline II.) the caffeine in green tea increases intracellular cAMP accumulation by inhibiting the enzyme, phosphodiesterase. See "How ECA Works" for more info on the importance of caffeine.

I have already discussed the effects of caffeine in several posts, so I will focus on COMT. Interestingly, the medical literature showing that green tea inhibits COMT dates back over two decades (7-NA). By inhibiting COMT, green tea prolongs the life of noradrenaline in the synaptic cleft. (This lets noradrenaline stimulate the receptors for a longer time before it is metabolized). The in vivo (human) study by Dulloo et al. (1) found that, compared to placebo and caffeine, green tea significantly increased total 24 hour urinary noradrenaline excretion. The researchers commented on the significance of this:

"This observation is consistent with the inhibiting effect of green tea on COMT, the consequential reduction in norepinephrine [noradrenaline] degradation, and hence, the spillover of norepinephrine into circulation, thereby accounting for the higher urinary excretion of norepinephrine. Such effects, resulting in a prolonged life of norepinephrine in the sympathetic synaptic cleft, could explain the observed effects of the extract in stimulating thermogenesis and fat oxidation" (1).

Written
Dec 2000
Last Update
Dec 2000
Discussion
Although this research is exciting, the fact remains that green tea does NOT normalize the release of noradrenaline (the primary obesity-causing defect) -- it prolongs the action of whatever amount of noradrenaline that your body is able to release. For this reason, Dulloo concluded that the thermogenic effect of green tea is "likely to be highly dependent upon the release of endogenous NA [noradrenaline]." Clearly, green tea (by itself) is going to be a "your mileage may vary" situation. However, tissue studies performed by Dulloo et al. showed that green tea produced a significant synergistic effect when it was combined with ephedrine or ephedrine/caffeine (2).

Since green tea prolongs the action of noradrenaline, you would think that it would have a stimulatory effect. However, Dulloo et al. noted that green tea caused no significant differences in heart rate. The most logical explanation for this is that the stimulatory effect of increased noradrenaline action is being countered by other mechanisms. For example, green tea contains the amino acid, theanine, which has been found to lower blood pressure (. Green tea also has a vasorelaxing effect (9, 10). One recent study found that regular tea consumption had no significant effect on blood pressure (11), but it is difficult to achieve a therapeutic dose without taking concentrated supplements. Further complicating the picture, however, is the fact that they also found that green and black tea caused a short term increase in blood pressure (11).

I hope there will be further research aimed at determining the optimal dosage for the ephedrine/caffeine/green tea combination. It seems likely that the addition of green tea will make it possible to normalize sympathetic tone with a less stimulating stack. In addition, green tea (without ephedrine/caffeine) may permit people with hypertension to obtain a mild increase in fat oxidation and thermogenesis. Clearly, additional research is needed to expand our understanding of the effect of green tea on blood pressure. Hypertensives that want to take green tea should definitely work with a doctor and monitor their blood pressure.

Green tea is an extremely logical supplement for obese people. In addition to its weight loss effect, green tea protects against a number of conditions that are VERY common among the obese:

Green tea has been found to reduce the risk of having a stroke (12, 13).
Green tea has anti-cancer and anti-tumor effects (14, 15).
Green tea can improve glucose/insulin levels and your blood lipid profile (16, 17, 18-NA, 19).
However, it is difficult to obtain all of these health benefits if one does not take green tea supplements -- without supplements, you would have to drink at least ten cups of green tea every day!


Green Tea Products
Green tea has so many health benefits that it's impossible to pick a single best product. The only logical way to evaluate green tea products is to separate them according to their suitability for specific purposes such as weight loss, blood pressure reduction, etc. If you are interested in green tea for cancer prevention and health enhancement, I would shoot for at least 10 cups of tea per day. That's a lot of tea! Perhaps a combination of supplements and drinking tea is the easiest way to consume enough tea.

For the price comparison, whenever possible, I calculated the price per 100 mg of polyphenols and the price per 100 mg of EGCG. These calculations make it easy to compare products with different size capsules and extracts that are standardized to different potencies. I was surprised to find that, based on polyphenol and EGCG content, there were huge price differences between products. For example, Natrol Green Tea Extract is only 3.6 cents per 100 mg of polyphenols; Natures Way Green Tea Extract is a whopping 28.21 cents.

Green Tea For Weight Loss
Research suggests that EGCG is the most important catechin for weight loss. Although most products specify the amount of polyphenols, only a few list the EGCG content. For weight loss purposes, the most powerful Green Tea extract is the standardized Green Tea Extract by NSI -- it contains a whopping 220 mg of EGCG per capsule. The second most powerful green tea extract is the Life Extension Super Green Tea Extract, which contains 122 mg of EGCG per capsule.

Apparently, all of these green tea extracts that are standardized to extremely high levels of EGCG contain very little caffeine. This is good if you are adding green tea to win ECA stack; however, if you are interested in using one of these high EGCG green tea supplements by itself, you'll get much better results if you take some caffeine with it.

Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J "Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans" Am J Clin Nutr 1999, Vol 70 (6), Pg 1040-5. PMID: 0010584049.

2.) Dulloo AG, Seydoux J, Girardier L, Chantre P, Vandermander J "Green tea and thermogenesis: interactions between catechin-polyphenols, caffeine and sympathetic activity" Int J Obes Relat Metab Disord 2000, Vol 24 (2), Pg 252-8. PMID: 0010702779.

3-BK.) Feldman, RS; Meyer, JS, and Quenzer, LF "Principles of Neuropsychopharmacology" Sinauer Associates, Inc. 1997.

4-NA.) Astrup A, Buemann B, Toubro S, Raben A "Defects in substrate oxidation involved in the predisposition to obesity" Proc Nutr Soc 1996, Vol 55 (3), Pg 817-28. PMID: 0009004326.

5-NA.) Astrup A, Raben A, Buemann B, Toubro S "Fat metabolism in the predisposition to obesity" Ann N Y Acad Sci 1997, Vol 827 Pg 417-30. PMID: 0009329772.

6.) Astrup A, Madsen J, Holst JJ, Christensen NJ "The effect of chronic ephedrine treatment on substrate utilization, the sympathoadrenal activity, and energy expenditure during glucose-induced thermogenesis in man" Metabolism 1986, Vol 35 (3), Pg 260-5. PMID: 0003512957.

7-NA.) Borchardt RT and Huber JA "Catechol O-methyltransferase. 5. Structure-activity relationships for inhibition by flavonoids" J Med Chem 1975, Vol 18 (1), Pg 120-2. PMID: 0001109569.

8.) Yokogoshi H, Kato Y, Sagesaka YM, Takihara-Matsuura T, Kakuda T, Takeuchi N "Reduction effect of theanine on blood pressure and brain 5- hydroxyindoles in spontaneously hypertensive rats" Biosci Biotechnol Biochem 1995, Vol 59 (4), Pg 615-8. PMID: 0007539642.

9.) Huang Y, Zhang A, Lau CW, Chen ZY "Vasorelaxant effects of purified green tea epicatechin derivatives in rat mesenteric artery" Life Sci 1998, Vol 63 (4), Pg 275-83. PMID: 0009698036.

10.) Huang Y, Chan NW, Lau CW, Yao XQ, Chan FL, Chen ZY "Involvement of endothelium/nitric oxide in vasorelaxation induced by purified green tea (-)epicatechin" Biochim Biophys Acta 1999, Vol 1427 (2), Pg 322-8. PMID: 0010216249.

11.) Hodgson JM, Puddey IB, Burke V, Beilin LJ, Jordan N "Effects on blood pressure of drinking green and black tea" J Hypertens 1999, Vol 17 (4), Pg 457-63. PMID: 0010404946.

12.) Sato Y, Nakatsuka H, Watanabe T, Hisamichi S, Shimizu H, Fujisaku S, Ichinowatari Y, Ida Y, Suda S, Kato K and others. "Possible contribution of green tea drinking habits to the prevention of stroke" Tohoku J Exp Med 1989, Vol 157 (4), Pg 337-43. PMID: 0002741170.

13.) Uchida S, Ozaki M, Akashi T, Yamashita K, Niwa M, Taniyama K "Effects of (-)-epigallocatechin-3-O-gallate (green tea tannin) on the life span of stroke-prone spontaneously hypertensive rats" Clin Exp Pharmacol Physiol Suppl 1995, Vol 1 Pg S302-3. PMID: 0009072402.

14.) Kono S, Ikeda M, Tokudome S, Kuratsune M "A case-control study of gastric cancer and diet in northern Kyushu, Japan" Jpn J Cancer Res 1988, Vol 79 (10), Pg 1067-74. PMID: 0003143695.

15.) Ruch RJ, Cheng SJ, Klaunig JE "Prevention of cytotoxicity and inhibition of intercellular communication by antioxidant catechins isolated from Chinese green tea" Carcinogenesis 1989, Vol 10 (6), Pg 1003-8. PMID: 0002470525.

16.) Karawya MS, Abdel Wahab SM, El-Olemy MM, Farrag NM "Diphenylamine, an antihyperglycemic agent from onion and tea" J Nat Prod 1984, Vol 47 (5), Pg 775-80. PMID: 0006512531.

17.) Muramatsu K, Fukuyo M, Hara Y "Effect of green tea catechins on plasma cholesterol level in cholesterol-fed rats" J Nutr Sci Vitaminol (Tokyo) 1986, Vol 32 (6), Pg 613-22. PMID: 0003585557.

18-NA.) Chisaka T, Matsuda H, Kubomura Y, Mochizuki M, Yamahara J, Fujimura H "The effect of crude drugs on experimental hypercholesteremia: mode of action of (-)-epigallocatechin gallate in tea leaves" Chem Pharm Bull (Tokyo) 1988, Vol 36 (1), Pg 227-33. PMID: 0003378286.

19.) Yokozawa T and Dong E "Influence of green tea and its three major components upon low-density lipoprotein oxidation" Exp Toxicol Pathol 1997, Vol 49 (5), Pg 329-35. PMID: 0009455677.

20-BK.) Greenspan, FS and Gardner, DG "Basic & Clinical Endocrinology" Lange Medical Books/McGraw-Hill 2000.

21-BK.) Munson, PL; Mueller, RA, and Breese, GR "Principles of Pharmacology. Basic Concepts & Clinical Applications." Chapman & Hall 1996.

22.) Deriaz O, Dionne F, Perusse L, Tremblay A, Vohl MC, Cote G, Bouchard C "DNA variation in the genes of the Na,K-adenosine triphosphatase and its relation with resting metabolic rate, respiratory quotient, and body fat" J Clin Invest 1994, Vol 93 (2), Pg 838-43. PMID: 0007509349.

November 30, 2001

Mechanism found for green tea in cancer fight

In research conducted at H. Lee Moffitt Cancer Center & Research Institute in Tampa Florida, a mechanism of green tea polyphenols' ability to cause the death of cancer cells was elucidated. By testing green tea polyphenols effect on prostate cancer cell lines, varying concentrations of the polyphenols were found to diminish a protein called Bcl-XL which protects cancer cells from apoptosis, which is programmed cell death.

Green tea has been shown to prevent several types of cancer in animal models. Human populations who consume green tea have lower rates of stomach, liver, pancreatic, breast, lung, esophageal and skin cancers.

Aslamuzzaman Kazi, PhD, research fellow in the Drug Discovery Program at Moffitt Cancer Center, described the finding: "The higher the concentration, the better the response - meaning more apoptosis, or programming that tells cells to die -- apparently occurring as a result of a greater decrease in Bcl-XL, a protein that protects cancer cells from apoptosis. At all concentrations, response was apparent within three hours."

Pin Dou, PhD, associate professor of oncology, biochemistry, and molecular biology at Moffitt further explained, "Because Bcl-XL is overexpressed in many cancers, it could be a key target in all these cancers and explain why green tea polyphenols (are) able to prevent human cancers in mouse models . . . Data from our laboratory suggests that at least one enzyme may modify Bcl-XL and that it is the actual target of tea. We also want to see if that target is present in all human cancers or just some of them."


Green tea has been shown to lower "bad" LDL cholesterol and serum triglyceride levels. Further, green tea's potent antioxidant effects inhibit the oxidation of LDL cholesterol in the arteries, which plays a major contributory role in the formation of atherosclerosis. "There is considerable epidemiological evidence that tea drinking lowers the risk of heart disease" (FEBS Lett., Aug. 1998, 433(1-2):44-46).

The cholesterol-lowering (hypocholesterolemic) effects of green tea (as well as black tea) have been confirmed by both animal and human epidemiological studies. High consumption of green tea by humans, especially more than 10 cups a day, was found to be associated with higher HDLs and lower LDL and VLDL cholesterol, as well as with various biomarkers indicating better liver health. Lower levels of lipid peroxides in the liver are one well-confirmed benefit of green-tea supplementation found in study after study.

A Japanese study relates, "Green tea catechin acts to limit the excessive rise in blood cholesterol" based on a series of studies reported in 1996 (Journal Nutritional Science Vitaminol., 32:613).

Additionally, some very exciting results were found when rats were fed 2.5% green tea leaves in their diet. The experimental group showed a drop in total cholesterol, low-density cholesterol, and triglycerides. The body weight of green tea-fed rats was 10 to 18% lower than that of rats not consuming green tea. In addition, the activity of antioxidant enzymes superoxide dismutase (SOD) and catalase, and of anticarcinogenic phase-II enzyme glutathione S-transferase (GST), were significantly higher in the green tea group, as was the glutathione level in the liver. There was no liver or kidney toxicity. Thus, the study demonstrated combined cardiovascular and anticancer effects of green tea.

The relation between green tea consumption and serum lipid concentrations were examined using cross-sectional data on 1306 males in Japan. Results indicated that total cholesterol levels were found to be inversely related to the consumption of green tea. "Adjusted mean concentrations of total cholesterol were significantly lower in men drinking nine cups or more a day than in those consuming zero to two cups a day" (Prev. Med. July 1992, 21(4):526-31). No wonder the Japanese people have the longest life span. Most Japanese sip tea all day long.

Green tea also has been shown to elevate levels of HDL, the good cholesterol that helps remove atherosclerotic plaque from arterial walls. Green tea is a natural ACE inhibitor. This is an extra benefit for those with high cholesterol and blood pressure, as published studies show lowered blood pressure in animals and humans given green tea extracts. We recommend one capsule (350 mg) of green tea 95% extract daily, or drinking one to ten cups of green or black tea a day.

Also maybe help burn cals...

A study has found: "Subjects spent 24 hours in a respiratory chamber designed to measure the rate calories were burned and energy expenditure. Those receiving the green tea experienced what researchers consider a significant increase in both tests. Tea extract subjects burned 4 percent more calories, and overall energy expenditure rose 4.5 percent."

BELTSVILLE, Md., Oct 10, 2002 (United Press International via COMTEX) -- Common tea can be an effective weapon in the fight against diabetes because it boosts insulin activity in the body by more than 15-fold, scientists at the U.S. Department of Agriculture said Thursday.

Insulin problems lie at the root of the potentially fatal illness diabetes, so researchers hope tea-based treatments will help treat or prevent the disease, which affects 17 million Americans. Not only that, this insulin-boosting phenomenon may explain why tea can help fight heart disease and high blood pressure as well.

"This is just one of the many well-established benefits that tea may have," researcher Richard Anderson, a biochemist at the USDA's Beltsville Human Nutrition Research Center in Maryland, told United Press International.

Tea has a long history as a folk remedy for diabetes in China, the West Indies and central Africa. Over the past 20 years scientists also have uncovered potential benefits from tea against cancer, high blood pressure and infection.

"Tea wasn't the only factor we looked at, but it was the best," Anderson said.

Anderson and his colleague Marilyn Polansky analyzed a host of herbs, spices and plants for any beneficial effect involving insulin, the hormone the body needs to convert sugar into energy. They took fat cells from rats and grew them in test tubes because fat cells are highly sensitive to insulin, Anderson explained. Then, they gave the cells mildly radioactive sugar, insulin, and various tea extracts. The radioactive sugar is easy to track and the more the extracts aided insulin activity, the more sugar the cells would convert.

The scientists found black, green and oolong teas boosted insulin activity the most. This insulin-augmenting effect was seen with both caffeinated and non-caffeinated teas, but not with herbal teas, which do not use leaves from tea bushes.

They also identified tea's most insulin-enhancing chemical, called epigallocatechin gallate. Adding whole or skim milk, nondairy creamers or soy milk appears to soak up tea's insulin-augmenting compounds and inhibit the insulin boost, although these milky sponges may release the tea extracts in the stomach, Anderson said. No absorption problem was seen with lemon juice.

"Hopefully people can get better simply by drinking tea," Anderson said. "These compounds clear from the body quite quickly, some in less than six hours, some less than four. The effects are not going to be that large, so you're going to need to continue drinking tea."

Anderson said his team also found cinnamon showed similar insulin-enhancing power. He suggests tea and cinnamon affects the cell proteins insulin binds to.

Diabetes is a disease where the body either does not make insulin or does not properly use it when it does produce it. The scientists think tea increases the body's sensitivity to insulin by setting off a chain reaction. As a result, the body attaches chemicals to insulin-binding proteins that enhance their activity.

Tea's insulin-boosting activity also might explain why tea seems to help prevent heart disease and high blood pressure, Anderson said. Medical investigators think high blood sugar damages blood vessels, and increasing insulin activity lowers blood sugar levels.

"This work seems to be truly new and extremely exciting," biochemist Anne-Marie Roussel at the Universite Joseph Fourier in Grenoble, France, told UPI. "This work is well done, and the data is promising not only to treat diabetes but perhaps also in preventing it." Roussel and Anderson added more tea studies need to be conducted with patients, not in lab models.

The scientists described their findings in a report published online by the Journal of Agricultural and Food Chemistry.

(Reported by Charles Choi, UPI Science News, in New York)

Copyright: Copyright 2002 by United Press International

By K.L. CAPOZZA, UPI Science News

SAN FRANCISCO, Mar 24, 2003 (United Press International via COMTEX) -- Long touted for its health-promoting properties, green tea might be an effective treatment for acne, a study suggests.

Green tea has been shown to fight bacteria, reduce inflammation and decrease hormone activity -- three characteristics that make the ancient tea an excellent candidate for an acne therapy.

"This study showed that 3 percent green tea cream is comparable to 4 percent benzoyl peroxide in the treatment of moderate to severe acne," said lead author, Dr. Jennifer Gan-Wong, with the Memorial Medical Center in the Philippines.

Gan-Wong presented her team's findings at the American Academy of Dermatology Annual Meeting. Researchers from tested the promising candidate -- in the form of a 3 percent green tea extract cream -- vs. the leading treatment for acne, 4 percent benzoyl peroxide cream.

A computer randomized a group of 108 subjects into one of two treatment groups. One applied benzoyl peroxide cream twice daily for 12 weeks and the other used green tea extract cream twice daily for the same period. Patients received identical bottles of cream and were unaware of the type of treatment they were assigned.

Subjects were examined and photographed each week by dermatologists, who also were unaware which treatment each patient had been given.

The researchers noted the green tea cream seemed to lighten patients' skin color and improve the overall appearance of their complexion.

Green tea therapy might be appealing to consumers because conventional wisdom holds that natural products are less toxic and have fewer side effects than other drug products, the researchers said.

The preliminary data suggest green tea extract cream causes fewer side effects than benzoyl peroxide treatment. Patients in the green tea group reported fewer cases of dry skin, itching and allergic responses.

The findings, while promising, are not yet substantial enough to change clinical practice, Dr. Azucena Arguelles, a private practice dermatologist from Mountain View, Calif., told United Press International.

"My sense is that for this to be out on the market and adopted by the medical community the results will need to be repeated," she said.

The finding could be relevant to the millions of Americans who suffer from acne breakouts, a condition which affects nearly 85 percent of the U.S. population and has a detrimental affect on self-esteem and well-being.

Green tea extract and aromatase activity

Green tea extract has been found to inhibit aromatase activity in male rats. (Aromatase is an enzyme that converts androgens to estrogens.) A recent study administered green tea extract catechins to male rats for two, four and eight weeks, starting at age five weeks. It was found that a 5% dose to male rats for two to eight weeks induced goiters and decreased weights of the body, testis and prostate gland. The treatment elevated circulating thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels, and decreased tri-iodothyronine and thyroxine levels (hormones secreted by the thymus gland). Green tea exhibited inhibitory effects on human placental aromatase activity. The endocrinological changes in the body were anti-thyroid effects and aromatase inhibition due to the effects of green tea extract and its components.

FOOD AND CHEMICAL TOXICOLOGY, 2002, Vol 40, Iss 7, pp 925-933

Green tea benefits digestive tract

Tea catechins undergo various metabolic changes after they are taken orally, though a large percentage is excreted intact with the feces. Epidemiological studies suggest a protective effect of tea against various human cancers, including colon and rectum. The bactericidal property of tea catechins plays several roles in the digestive tract. In the small intestine, catechins inhibit alpha-amylase activity, and a certain amount is absorbed into the portal vein. Although catechins are bactericidal, they do not affect lactic acid bacteria. Including tea catechins in the diet for several weeks decreases putrefactive products and increases organic acids by lowering pH. These changes were achieved with 100 mg of tea catechins (equivalent to two to five cups of green tea) three times daily with meals for three weeks. When catechin administration ceased, the effects reversed after one week. Catechins should be considered further in colon carcinogenesis studies.

JOURNAL OF CELLULAR BIOCHEMISTRY, 1997, Suppl. 27, pp 52-58


The inhibitory action of tea polyphenols towards the development and growth of bacterial spores was examined. The heat resistance of B stearothermophilus spores (a thermophilic spore-forming bacterium) was reduced by the addition of tea polyphenols. Clostridium thermoaceticum, an anaerobic spore-forming bacterium, also exhibited reduced heat resistance of its spores in the presence of tea polyphenols. Epigallocatechin gallate, the main component of tea polyphenols, showed strong activity against both B stearothermophilus and C thermoaceticum. The heat resistance of these bacterial spores was more rapidly decreased by the addition of tea polyphenols at high temperatures.

JOURNAL OF BIOSCIENCE AND BIOENGINEERING, 2000, Vol 90, Iss 1, pp 81-85

Green tea protects against alcohol-induced liver injury

A study examined the antioxidant polyphenolic extract of green tea against early alcohol-induced liver injury. Rats were fed high-fat liquid diets with or without alcohol and green tea (300 mg kg/day) continuously for four weeks. After four weeks, the blood ALT (sign of liver damage) levels were increased significantly from 35 to 114 (four-fold over placebo group values). However, the inclusion of green tea extract in the diet significantly blunted the increase to 65. The alcohol also caused severe fatty accumulation, mild inflammation and tissue death in the liver. However, with green tea extract, the increase in tissue death caused by alcohol were significantly reduced, while not affecting fat accumulation or inflammation. Alcohol also significantly increased the accumulation of protein adducts (products of lipid peroxidation and an indication of oxidative stress). However, green tea extract blocked this effect almost completely. Green tea extract also blunted the increase of TNFalpha (causes inflammation) protein levels in the liver by alcohol. The results indicate that dietary antioxidants, such as those found in green tea, prevent early alcohol-induced liver injury, most likely by preventing free radical stress.

BIOLOGICAL CHEMISTRY 2002;383(3-4):663-70

Green tea, grape juice, and colon cancer
Full source: BIOLOGICAL & PHARMACEUTICAL BULLETIN, 2000, Vol 23, Iss 6, pp 695-699

A study reported the effects of tea and juice on the activity of the intestines. Green tea strongly inhibited the E. coli-expressed mouse intestinal phenol sulfotransferases (P-STs) activity in vitro. The active component of green tea, (-)-Epigallocatechin gallate (EGCG), was found to be the most potent inhibitor among the catechins tested. (-)EGCG also inhibited the P-ST activity of the human colon cancer cells. Among fruit juices examined (apple, grape, grapefruit and orange), grape juice exhibited the most potent inhibitory action on the P-ST activity of mouse intestines and human colon cancer cells. The inhibitory activity of grape juice was located mainly in the skin and seeds. Flavonols, such as quercetin and kaempferol, inhibited the P-ST activity at low concentrations. The results suggest the possible inhibition of P-ST activity in human intestines by green tea or grape juice.

Curr Med Chem Anti-Canc Agents 2002 Jul;2(4):441-63 Related Articles, Links


Green tea catechins as novel antitumor and antiangiogenic compounds.

Demeule M, Michaud-Levesque J, Annabi B, Gingras D, Boivin D, Jodoin J, Lamy S, Bertrand Y, Beliveau R.

Laboratoire de Medecine Moleculaire, UQAM-Hocric;pital Sainte-Justine, Montreal, Canada. [email protected]

The concept of cancer prevention by use of naturally occuring substances that could be included in the diet is under investigation as a practical approach towards reducing cancer incidence, and therefore the mortality and morbidity associated with this disease. Tea, which is the most popularly consumed beverage aside from water, has been particularly associated with decreased risk of various proliferative diseases such as cancer and atherosclerosis in humans. Various studies have provided evidence that polyphenols are the strongest biologically active agents in green tea. Green tea polyphenols (GTPs) mainly consist of catechins (3-flavanols), of which (-)-epigallocatechin gallate is the most abundant and the most extensively studied. Recent observations have raised the possibility that green tea catechins, in addition to their antioxidative properties, also affect the molecular mechanisms involved in angiogenesis, extracellular matrix degradation, regulation of cell death and multidrug resistance. This article will review the effects and the biological activities of green tea catechins in relation to these mechanisms, each of which plays a crucial role in the development of cancer in humans. The extraction of polyphenols from green tea, as well as their bioavailability, are also discussed since these two important parameters affect blood and tissue levels of the GTPs and consequently their biological activities. In addition, general perspectives on the application of dietary GTPs as novel antiangiogenic and antitumor compounds are also presented.

PMID: 12678730 [PubMed - in process]

Kidney Int 2003 May;63(5):1785-1790 Related Articles, Links


Effect of green tea extract on cardiac hypertrophy following 5/6 nephrectomy in the rat.

Priyadarshi S, Valentine B, Han C, Fedorova OV, Bagrov AY, Liu J, Periyasamy SM, Kennedy D, Malhotra D, Xie Z, Shapiro JI.

The Departments of Medicine and Pharmacology Medical College of Ohio, Toledo, Ohio; The Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medical Sciences, Beijing, China; and Laboratory of Cardiovascular Science,National Institute on Aging, National Institutes of Health, Baltimore, Maryland.

Effect of green tea extract on cardiac hypertrophy following 5/6 nephrectomy in the rat. BACKGROUND: Left ventricular hypertrophy commonly complicates chronic renal failure. We have observed that at least one pathway of left ventricular hypertrophy appears to involve signaling through reactive oxygen species (ROS). Green tea is a substance that appears to have substantial antioxidant activity, yet is safe and is currently widely used. We, therefore, studied whether green tea supplementation could attenuate the development of left ventricular hypertrophy in an animal model of chronic renal failure. METHODS: Male Sprague-Dawley rats were subjected to sham or remnant kidney surgery and given green tea extract (0.1% and 0.25%) or plain drinking water for the next 4 weeks. Heart weight, body weight, and cardiac Na-K-ATPase activity were measured at the end of this period. To further test our hypothesis, we performed studies in cardiac myocytes isolated from adult male Sprague-Dawley rats. We measured the generation of ROS using the oxidant sensitive dye dichlorofluorescein (DCF) as well as (3H)phenylalanine incorporation following exposure to cardiac glycosides with and without green tea extract. RESULTS: Administration of green tea extract at 0.25% resulted in attenuation of left ventricular hypertrophy, hypertension, and preserved cardiac Na-K-ATPase activity in rats subjected to remnant kidney surgery (all P < 0.01). In subsequent studies performed in isolated cardiac myocytes, both ouabain and marinobufagenin (MBG) were both found to increase ROS production and (3H)phenylalanine incorporation at concentrations substantially below their inhibitor concentration (IC) 50 for the sodium pump. Addition of green tea extract prevented increases in ROS production as well as (3H)phenylalanine incorporation in these isolated cardiac myocytes. CONCLUSION: Green tea extract appears to block the development of cardiac hypertrophy in experimental renal failure. Some of this effect may be related to the attenuation of hypertension, but a direct effect on cardiac myocyte ROS production and growth was also identified. Clinical studies of green tea extract in chronic renal failure patients may be warranted.

PMID: 12675854 [PubMed - as supplied by publisher]

Toxicol Lett 2003 Apr 11;140-141:125-32 Related Articles, Links


Defenses against peroxynitrite: selenocompounds and flavonoids.

Klotz LO, Sies H.

Institut fur Physiologische Chemie I, Heinrich-Heine-Universitat Dusseldorf, Postfach 101007, D-40001, Dusseldorf, Germany

The inflammatory mediator peroxynitrite, when generated in excess, may damage cells by oxidizing and nitrating cellular components. Defense against this reactive species may be at the level of prevention of the formation of peroxynitrite, at the level of interception, or at the level of repair of damage caused by peroxynitrite. Several selenocompounds serve this purpose and include selenoproteins such as glutathione peroxidase (GPx), selenoprotein P and thioredoxin reductase, or low-molecular-weight substances such as ebselen. Further, flavonoids, such as (-)-epicatechin, which occurs in green tea or cocoa as monomer or in the form of oligomers, can contribute to cellular defense against peroxynitrite.

PMID: 12676458 [PubMed - in process]

Phytother Res 2003 Mar;17(3):206-9 Related Articles, Links


Protective effect of green tea polyphenol (-)-epigallocatechin gallate and other antioxidants on lipid peroxidation in gerbil brain homogenates.

Lee SR, Im KJ, Suh SI, Jung JG.

Department of Pharmacology, School of Medicine and Brain Research Institute, Keimyung University, Taegu, South Korea.

The aim of this study was to compare the protective effects of green tea polyphenol (-)-epigallocatechin gallate (EGCG) and other well-known antioxidants on the lipid peroxidation in gerbil brain homogenates. Oxidative stress was induced by H(2)O(2) (10 mM) or ferrous ammonium sulfate (5 micro M) and lipid peroxidation was studied. Hydrogen peroxide and ferrous ions are capable of oxidizing a wide range of substrates and causing biological damage. The reaction, referred to as the Fenton process, is complex and can generate both hydroxyl radicals and higher oxidation states of the iron. Thiobarbituric acid-reactive substances (TBA-RS) were used as a marker of lipid peroxidation. EGCG, trolox, lipoic acid, and melatonin reduced H(2)O(2)- or ferrous ion-induced lipid peroxidation in a concentration-dependant manner. In reducing the H(2)O(2)-induced lipid peroxidation, IC(50) values of antioxidants were as follows: EGCG (0.66 micro M), trolox (37.08 micro M), lipoic acid (7.88 mM), and melatonin (19.11 mM). In reducing the ferrous ion-induced lipid peroxidation, IC50 values of antioxidants were as follows: EGCG (3.32 micro M), trolox (75.65 micro M), lipoic acid (7.63 mM), and melatonin (15.48 mM). Under the in vitro conditions of this experiment, EGCG was the most potent antioxidant in inhibiting H(2)O(2) or ferrous ion-induced lipid peroxidation in the gerbil brain homogenates. Copyright 2003 John Wiley & Sons, Ltd.

PMID: 12672147 [PubMed - in process]

J Environ Biol 2002 Oct;23(4):373-6 Related Articles, Links


An anticlastogenic in vivo micronucleus assay for tea.

Edwin D, Geetha VR, Vishwanathan H, Usha Rani MV.

Department of Environmental Sciences, Bharathiar University, Coimbatore-641 046, Tamil Nadu, India. [email protected]

Common use of antimutagens and anticarcinogens in everyday life is an effective measure for preventing human cancer and genetic diseases. Antioxidant properties of tea have vast potential as protective agents against diverse toxic effects. The present study was aimed to evaluate the role of aqueous clonal tea extracts (green tea, oolong tea and black tea) in modulating the genotoxic damage induced by cyclophosphamide (CP), a commonly used chemotherapeutic drug and a well-known mutagen and clastogen. All the three tea extracts at 1 and 2% concentration did not increase the frequency of micronucleated polychromatic erythrocytes (MPE) in bone marrow cells of mice when administered individually. The tea extracts decreased the micronuclei (MN) induced by CP. Therefore, regular intake of tea may improve the antioxidant status in in vivo and thereby reduce the risk of cancer and coronary heart disease.

PMID: 12674376 [PubMed - in process]


Food Chem Toxicol 2002 Jul;40(7):925-33

Inhibition of aromatase activity by green tea extract catechins and their endocrinological effects of oral administration in rats.

Satoh K, Sakamoto Y, Ogata A, Nagai F, Mikuriya H, Numazawa M, Yamada K, Aoki N.

We orally administered polyphenone-60 (P-60), green tea extract catechins, in the diet (0, 1.25 and 5%) to male rats for 2, 4 and 8 weeks initiated at 5 weeks old. It was found that a 5% dose to male rats for 2-8 weeks induced goiters and decreased weights of the body, testis and prostate gland. Endocrinologically, elevating plasma thyroid stimulating hormone (TSH), luteinizing hormone (LH) and testosterone levels and decreasing tri-iodothyronine (T(3)) and thyroxine (T(4)) levels were induced by this treatment. We also found that P-60 as a whole and some of its constituents exhibited inhibitory effects on human placental aromatase activity by in vitro assay. The concentration of P-60 that required producing 50% inhibition of the aromatase activity (IC(50) value) was 28 microg/ml. The IC(50) values of (-)-catechin gallate (Cg), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCg) and (-)-gallocatechin gallate (GCg) were 5.5 x 10(-6), 1.0 x 10(-4), 6.0 x 10(-5) and 1.5 x 10(-5) M, respectively. (-)- Epicatechin gallate (ECg) at 1.0 x 10(-4) M produced 20% inhibition. (-)-Epicatechin (EC) and (+)-catechin (CT) exhibited no effects on aromatase activity. The endocrinological changes observed in vivo were in conformity with antithyroid effects and aromatase inhibition effects of P-60 and its constituents.


freshen breath too
In the first study, conducted at Pace University, green tea extracts were mixed with several different kinds of bacteria, including those that cause strep throat and tooth decay. The researchers found that green tea was effective at fighting bacteria by inhibiting their growth.


"Our research shows tea extracts can destroy the organism that causes disease," says lead researcher Milton Schiffenbauer, PhD, a microbiologist and biology professor at Pace University in New York City, in a news release.


In fact, the same study suggests that green tea boosts the effectiveness of toothpaste and mouthwash in fighting viruses. Toothpaste and mouthwash had very little virus-fighting effect when mixed with bacteria; however, when green tea extract was added, 99% to 100% of the bacteria disappeared.


What's responsible for the health benefits of tea? Teas contain polyphenols, which are antioxidants that protect human cells from damage. Flavonids are a group of polyphenols that occur naturally in tea. It is suspected that high levels of these polyphenols in the body can fight viruses as well as cancer, including pancreas, colon, bladder, prostate, and breast cancer.


In the "bad breath" study, researchers combined black tea extracts with three species of bacteria (all linked with bad breath) in petri dishes for 48 hours. They compared the results with bacteria that sat alone.


In all cases, tea polyphenols inhibited the growth of bacteria by 30% and reduced the production of compounds that cause bad breath.


The study suggests that rinsing with black tea keeps plaque from forming and destroys acids that cause tooth decay.


"Besides inhibiting the growth of pathogens in the mouth, black tea and its polyphenols may benefit human oral health by suppressing the bad-smelling compounds that these pathogens produce," says lead researcher Christine D. Wu, PhD, professor of periodontics at the University of Illinois, Chicago, in a news release.


Both studies detailing health benefits of tea were presented at the annual American Society for Microbiology General Meeting held in Washington, D.C., this week.



Medical College of Georgia
**broken link removed**

Green Tea Linked to Skin Cell Rejuvenation

Christine Hurley Deriso

Research into the health-promoting properties of green tea is yielding
information that may lead to new treatments for skin diseases and
wounds.

Dr. Stephen Hsu, a cell biologist in the Medical College of Georgia
Department of Oral Biology, has uncovered a wealth of information
about green tea in the last few years. Most importantly, he helped
determine that compounds in green tea called polyphenols help
eliminate free radicals, which can cause cancer by altering DNA. He
also found that polyphenols safeguard healthy cells while ushering
cancer cells to their death.

He recently began studying the most abundant green tea polyphenol,
EGCG. Using pooled human keratinocytes (skin cells), he and his
colleagues studied the normal growth of the skin cells and compared it
to the growth of the cells when exposed to EGCG.

To their astonishment, they found that EGCG reactivated dying skin
cells. "Cells that migrate toward the surface of the skin normally
live about 28 days, and by day 20, they basically sit on the upper
layer of the skin getting ready to die," Dr. Hsu said. "But EGCG
reactivates them. I was so surprised."

The skin consists of three layers: the epidermis (outer layer), dermis
(mid-layer) and hypodermis (inner layer). Dr. Hsu learned that green
tea polyphenols aren’t absorbed beyond the epidermis, so any benefits
are limited to that outer layer of skin. But the benefits, he
stressed, seem significant.

Cells in the epidermis, or keratinocytes, are in a constant state of
renewal. The newly formed cells, stem cells, are undifferentiated but
rapidly dividing. As they push through the epidermis, they begin
differentiating. During this migration and differentiation process,
the cells are very active, expending and consuming vast amounts of
energy.

Once they reach the surface of the skin, their metabolic activity
slows dramatically and they prepare to die, while forming a
water-proof, sheet-like structure. As they die off about a month into
their life cycle, they are replaced by another wave of migrating cells
supplied by stem cells, starting the process all over again.

But EGCG seems to be a fountain of youth for skin cells. "When exposed
to EGCG, the old cells found in the upper layers of the epidermis
appear to start dividing again," Dr. Hsu said. "They make DNA and
produce more energy. They are reactivated. There are lots of
unknowns--this is the first step into the door--but if we can energize
dying skin cells, we can probably improve the skin condition."

In addition, the researchers found that EGCG accelerates the
differentiation process among new cells.

Combining these effects of EGCG on skin cells in different layers of
the epidermis, Dr. Hsu noted potential benefits for skin conditions as
diverse as aphthous ulcers, psoriasis, rosascea, wrinkles and wounds.
"If skin cells surrounding wounds or infections don’t heal in time,
fibroblasts in the connective tissue may rush in to fill the void and
cause scar tissue formation," he said. "If we can spur the skin cells
to differentiate and proliferate, we can potentially accelerate the
wound-healing process and prevent scarring."

This potential benefit is particularly exciting for conditions such as
diabetes, which stubbornly inhibits the wound-healing process, Dr. Hsu
said.

He and his colleagues hope to identify dermatologists interested in
collaborating on clinical studies of EGCG and other polyphenols on
patients.

Dr. Hsu’s research, which is excerpted on the online version of the
Journal of Pharmacology and Experimental Therapeutics, is funded by
the Dental Research Foundation, the MCG School of Dentistry and MCG
Research Institute.

The abstract...

J Pharmacol Exp Ther 2003 Mar 27; [epub ahead of print]

Green Tea Polyphenols Induce Differentiation and Proliferation in
Epidermal Keratinocytes.

Hsu SD, Bollag WB, Lewis J, Huang Q, Singh B, Sharawy M, Yamamoto T,
Schuster G.

Medical College of Georgia.

The most abundant green tea polyphenol, epigallocatechin-3-gallate
(EGCG), was found to induce differential effects between tumor cells
and normal cells. Nevertheless, how normal epithelial cells respond to
the polyphenol at concentrations for which tumor cells undergo
apoptosis is undefined. The current study tested exponentially growing
and aged primary human epidermal keratinocytes in response to EGCG or
a mixture of the four major green tea polyphenols. EGCG elicited cell
differentiation with associated induction of p57/KIP2 within 24 hours
in growing keratinocytes, measured by the expression of keratin 1,
filaggrin and transglutaminase activity. Aged keratinocytes, which
exhibited low basal cellular activities after culturing in growth
medium for up to 25 days, renewed DNA synthesis and activated
succinate dehydrogenase up to 37-fold upon exposure to either EGCG or
the polyphenols. These results suggest that tea polyphenols may be
used for treatment of wounds or certain skin conditions characterized
by altered cellular activities or metabolism.

PMID: 12663686 [PubMed - as supplied by publisher]

**broken link removed**


flouride
fluoride levels in extract might be lower than leaf:
**broken link removed**

I'm also not aware of evidence of fluorosis linked to tea
consumption (except Tibetan "brick tea"). Although there's
evidence of a correlation between improved bone density and
tea drinking, which might be attributed to fluoride content:

Arch Intern Med 2002 May 13;162(9):1001-6:
"CONCLUSION: Habitual tea consumption, especially for more
than 10 years, has significant beneficial effects on BMD
of the total body, lumbar spine, and hip regions in adults."

**broken link removed**


Recent studies suggest the exract is not as good as the brew but may be even better. My boy Instynct has very high ECGC content pills. Much easier pop a few pills a day they brewing GT all day.

Scientists in the United States and Switzerland may have found two more uses for green tea. Studies published in the December 1999 issues of the American Journal of Clinical Nutrition5 and Urology6 show that substances which are abundant in green tea extracts may promote weight loss and treat prostatitis, a painful urinary condition.

Dr. Abdul Dulloo led the research into weight loss, which was conducted at the University of Geneva. Dulloo's team studied the effects of green tea on ten healthy young men (average age: 25) who ranged in body type from "lean" to "mildly overweight."

The study's participants were put on a "typical Western diet" of about 13% protein, 40% fat and 47% carbohydrates. For six weeks, the men took two capsules consisting of either green tea extract plus 50 milligrams of caffeine; 50 milligrams of caffeine alone; or a placebo with each meal.

Three times during the study, researchers measured the men's energy expenditure (EE - the number of calories used in a 24-hour period) in a respiratory chamber. They also gauged the men's respiration quotient, or RQ. (RQ is a measurement of how well the body utilizes carbohydrates, proteins and fats. A lower RQ means that more fats are being metabolized by the body for energy.)

Results showed that those men taking the green tea extract experienced "a significant increase in 24-h EE" and "a significant decrease in 24-h RQ" over those taking only caffeine or the placebo. Men taking the green tea extract also used more fat calories than those using the placebo.

There was no difference between caffeine users and placebo users in terms of fat calorie burning or overall calorie burning. The scientists surmised that substances known as catechin polyphenols in the green tea extract may alter the body's use of norepinephrine, a chemical transmitter in the nervous system, to increase the rate of calorie burning.

In their conclusion, the scientists stated, "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."

Perhaps most importantly, the scientists noted that use of green tea extract was "not accompanied by an increase in heart rate. This leaves open the possibility of using green tea as an alternative to stimulant-based diet drugs, which may cause adverse effects on obese individuals and patients with hypertension and other cardiovascular conditions.

While Dulloo's team studied the effects of catechin polyphenols, researchers in the U.S. looked at the possible benefits of another substance found in green tea - a bioflavanoid known as quercetin - to combat nonbacterial chronic prostatitis.

Also known as pelvic pain syndrome, prostatitis is an inflammation of the prostate gland that affects approximately 30 million men in the U.S. The condition causes severe urogenital pain, and the standard treatment regimen of antibiotics offers little to no success.

A team of scientists at the Institute for Male Urology in Encino, California headed by Dr. Daniel Shoskes conducted a double-blind, placebo-controlled trial by first dividing 30 men with chronic prostatitis into two groups. One group received 500 mg of quercetin twice daily for one month, while the other group received a placebo.

A National Institutes of Health scoring system was used to grade the subjects' symptoms and quality-of-life impact at the beginning and conclusion of the study. Sixty-seven percent of patients who received quercetin had an improvement of symptoms of at least 25%, compared to only 20% of the placebo group. In addition, symptom scores of those taking quercetin improved an average of nearly eight points, while those in the placebo group improved by just 1.4 points.

In an unblinded followup study, 17 additional men received a supplement containing quercetin, as well as a mixture of bromelain and papain to enhance bioflavanoid absorption. Eighty-two percent of patients receiving the quercetin-bromelain-papain combination had at least a 25% improvement in their symptom scores.

While consuming mass quantities of green tea may not cure prostatitis, the scientists did conclude that "therapy with the bioflavonoid quercetin is well tolerated and provides significant symptomatic improvement in most men with chronic pelvic pain syndrome." Dr. Shoskes added that the study's findings "offer hope to the millions of men who suffer from this poorly understood and painful condition, as it provides a new option for doctors who've been frustrated by limited treatment choices."

References

Hirose M. Inhibition of mammary gland carcinogenesis by green tea catechins. Cancer Lett 1994;83:149-156.
Gao YT. Reduced risk of esophageal cancer associated with green tea consumption. J Natl Cancer Inst 1994;86:855-858.
Muhtar H. Tea components: antimutagenic and anticarcinogenic effects. Prev Med 1992;21:351-360.
Toda M. Antibacterial and bactericidal activities of Japanese green tea. Nippon Saikingaku Zasshi 1989;44:669-672.
Dulloo A, et al. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Amer J Clin Nutr 1999;70:1040-45.
Shoskes D, et al. Quercetin in men with category III chronic prostatitis: a preliminary prospective, double-blind, placebo-controlled trial. Urology December 1999;54(6):960-963.




http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=12918062&dopt=Abstract

Epigallocatechin-3-gallate is a potent natural inhibitor of fatty acid synthase in intact cells and selectively induces apoptosis in prostate cancer cells.

Brusselmans K, De Schrijver E, Heyns W, Verhoeven G, Swinnen JV.

Laboratory for Experimental Medicine and Endocrinology, Department of Developmental Biology, Gasthuisberg, Catholic University of Leuven, Leuven, Belgium.

Chemical inhibitors of fatty acid synthase (FAS) inhibit growth and induce apoptosis in several cancer cell lines in vitro and in tumor xenografts in vivo. Recently the green tea component epigallocatechin-3-gallate (EGCG) was shown to act as a natural inhibitor of FAS in chicken liver extracts. Here we investigated whether EGCG inhibits FAS activity in cultured prostate cancer cells and how this inhibition affects endogenous lipid synthesis, cell proliferation and cell viability. The high levels of FAS activity in LNCaP cells were dose-dependently inhibited by EGCG and this inhibition was paralleled by decreased endogenous lipid synthesis, inhibition of cell growth and induction of apoptosis. In contrast, epicatechin (EC), another closely related green tea polyphenolic compound, which does not inhibit FAS, had no effect on LNCaP cell growth or viability. Treatment of nonmalignant cells with low levels of FAS activity (fibroblasts) with EGCG led to a decrease in growth rate but not to induction of apoptosis. These data indicate that EGCG inhibits FAS activity as efficiently as presently known synthetic inhibitors and selectively causes apoptosis in LNCaP cells but not in nontumoral fibroblasts. These findings establish EGCG as a potent natural inhibitor of FAS in intact cells and strengthen the molecular basis for the use of EGCG as a chemopreventive and therapeutic antineoplastic agent. Copyright 2003 Wiley-Liss, Inc.

PMID: 12918062 [PubMed - indexed for MEDLINE]



Researchers theorize that one of the Green Tea's mechanism of action relies on the synergy between EGCG and caffeine. Green Tea's catechons ( a subclass of flavonoids) and caffeine work by:

1. Inhibiting the enzyme, catechol O-methyltransferase (COMT), which is responsible for breaking down noreinephrine, thus increasing this neurotransmitter's life in the synaptic cleft.

2. Inhibiting phosphodiesterases, thus increasing the life of cyclic AMP (cAMP) in the cell.

Together, these effects heighten the impact of norepinephrine is the neurotransmitter which plays a large role in the control of thermogenesis and fat oxidation for weight loss.

More on GT

Quote:

several national tea researchers and dietary supplement experts say the metabolism claims for tea are based on a few small studies, and they argue that the verdict is still out. "The studies are suggestive but not conclusive on tea's effect on metabolism," says Mark Blumenthal, founder of the American Botanical Council.

The research includes:

A study of 12 normal-weight men, conducted by Department of Agriculture researchers. It showed that when the men drank five cups of water with caffeine in eight hours, they had a 3.4% increase in calories burned in a 24-hour period compared with drinking plain water. When they drank five cups of oolong (dark) tea containing the same amount of caffeine, they had a 2.9% increase in calories burned. The difference between the tea and the caffeinated water was not statistically significant.
After drinking the tea, they also experienced an increase in the amount of body fat that was used as fuel, suggesting that the caffeine and other components of tea may mobilize fat stores for use as energy, experts say.

A study of 10 healthy young men conducted by Swiss researchers showed a roughly 3% to 4% increase in calories burned for men taking green tea extract and caffeine over those taking caffeine alone or a placebo. They also found an increase in the use of fat as fuel for those consuming the green tea extract.
"Anything we find with tea will probably be a small effect," says Beverly Clevidence, a research nutritionist at the USDA's Diet and Human Performance Laboratory in Beltsville, Md., who worked on the USDA study.

"In our study, men burned, on average, an additional 65 calories during the day that they drank the five cups of oolong tea. Scientists aren't sure whether it's the caffeine or the components called catechins in tea that may cause the metabolic increase," she says.

damn ... gread articles!

On a personal note I would like to add that:

I like to take BOTH the brew and the extract (not necessarily at the same time). Particularly interesting is dumping Theanine into the brew for a nice alert yet relaxed state.

Alot of people dislike the taste of GT and I cant stand 90% of the brands out thre myself. However one brand I find very pleasing to the taste buds is here: **broken link removed**

And no I dont have any finicial ties with them