Green Tea Research

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Polyphenols isolated from green tea leaves - Epigallocatechin Gallate (EGCG)

Comment by Dr. Wendy Wells, NMD

One of the methods of action of the EGCG is very similar to methotrexate, with less side effects. Methotrexate is a chemotherapeutic agent that inhibits DNA synthesis of fast growing cells (cancer). It inhibits the enzyme dihydrofolate reductase (DHFR), which cancer cells need to be able to grow. There are many cells in our body that are fast growing, namely the cells lining the gastrointestinal tract and those of a growing fetus. I would like to caution anyone who is pregnant, or has colitis, ulcers, diverticulitis, GERD, or patients on long term prednisone/steroids for asthma or other inflammatory conditions, from taking ECGC in high quantities. Drinking a cup of tea is quite acceptable, much more than taking a handful of ECGC supplements. As always, I suggest consulting a physician well versed in the research based natural medicines.

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Bioavailability and antioxidant activity of tea flavanols after consumption of green tea, black tea, or a green tea extract supplement.

Am J Clin Nutr. 2004 Dec;80(6):1558-64.

Henning SM, Niu Y, Lee NH, Thames GD, Minutti RR, Wang H, Go VL, Heber D.
Center for Human Nutrition, David Geffen School of Medicine and the Department of Biostatistics, School of Public Health, University of California, Los Angeles, 90095, USA.

BACKGROUND: Green and black tea polyphenols have been extensively studied as cancer chemopreventive agents. Many in vitro experiments have supported their strong antioxidant activity. Additional in vivo studies are needed to examine the pharmacokinetic relation of absorption and antioxidant activity of tea polyphenols administered in the form of green or black tea or tea extract supplements. OBJECTIVE: The purpose of this study was to compare the pharmacokinetic disposition of tea polyphenols and their effect on the antioxidant capacity in plasma 8 h after a bolus consumption of either green tea, black tea, or a green tea extract supplement. DESIGN: Thirty healthy subjects were randomly assigned to 3 different sequences of green tea, black tea, or a green tea extract supplement in a 3 x 3 crossover design with a 1-wk washout period in between treatments. RESULTS: Flavanol absorption was enhanced when tea polyphenols were administered as a green tea supplement in capsule form and led to a small but significant increase in plasma antioxidant activity compared with when tea polyphenols were consumed as black tea or green tea. All 3 interventions provided similar amounts of (-)-epigallocatechin-3-gallate. CONCLUSIONS: Our observations suggest that green tea extract supplements retain the beneficial effects of green and black tea and may be used in future chemoprevention studies to provide a large dose of tea polyphenols without the side effects of caffeine associated with green and black tea beverages.

Effectiveness of moderate green tea consumption on antioxidative status and plasma lipid profile in humans.

J Nutr Biochem. 2005 Mar;16(3):144-9.

Erba D, Riso P, Bordoni A, Foti P, Biagi PL, Testolin G. Department of Food Science and Microbiology, University of Milan, 20133 Milan, Italy.

The antioxidant activity of green tea has been extensively studied; however, the results obtained from dietary intervention studies are controversial. In the present study we investigated the effect of the addition of two cups of green tea (containing approximately 250 mg of total catechins) to a controlled diet in a group of healthy volunteers with respect to a group following the same controlled diet but not consuming green tea. Antioxidant status and lipid profile in plasma, the resistance from oxidative damage to lipid and DNA, and the activity of glutathione peroxidase (GPX) in isolated lymphocytes were measured at the beginning and the end of the trial. After 42 days, consumption of green tea caused a significant increase in plasma total antioxidant activity [from 1.79 to 1.98 mumol Trolox equivalent (TE)/ml, P<.001], significant decreases in plasma peroxides level (from 412 to 288 Carr U, P<.05) and induced DNA oxidative damage in lymphocytes (from 14.2% to 10.1% of DNA in tail, P<.05), a moderate although significant decrease in LDL cholesterol (from 119.9 to 106.6 mg/dL, P<.05) with respect to control. The present study suggests the ability of Green Tea, consumed within a balanced controlled diet, to improve overall the antioxidative status and to protect against oxidative damage in humans.

Green tea polyphenols inhibit oxidant-induced DNA strand breakage in cultured lung cells.

Free Radic Biol Med, 310(6981):235-42 1997

The influence of green tea polyphenols (GTP) on the formation of DNA strand breaks (DNA-SB) and lipid peroxidation products (LPP) in cultured human lung cells (A 549) exposed to different oxidants was investigated. Cells were pretreated with GTP for 2 h and then exposed to cigarette smoke solution, H2O2 or FeCl3 for 30 min. After exposure, the cells were analyzed for DNA-SB, LPP, and viability. In addition, the effects of GTP added directly to the incubation mixtures during exposure were examined, using the same end points. It appeared that pretreatment with GTP inhibited both cigarette smoke- and H2O2-induced DNA breakage; i.e., following exposure to cigarette smoke or H2O2, the fraction of DNA passing through a microfilter increased significantly in cells not subjected to GTP, but this effect was prevented or inhibited in GTP-treated cells. Pretreatment with GTP also reduced the overall toxicity of H2O2 as determined by cell growth after exposure. Moreover, addition of GTP during exposure reduced both cigarette smoke- and H2O2-induced DNA breakage as well as formation of LPP after exposure to Fe3+. These results indicate that GTP inhibit the formation of DNA-SB in cells exposed to oxidants. It is possible that this ability to GTP to inhibit DNA-SB formation might contribute to the antitumorogenic properties of green tea. Learn more about the effects of Green Tea Polyphenols

NSI Green Tea Extract 500 mg - 100 Caps

Green tea is a natural source of antioxidants, which neutralize harmful molecules in the body known as free radicals. Researchers have found that epigallocatechin gallate (EGCG), an antioxidant-like compound found in green tea, is over 200 times more powerful than vitamin E in neutralizing pro-oxidants and free radicals.Studies have already shown that green tea may lead to a lower risk of skin, lung and prostate cancer, but now, it appears that the nutrient’s EGCG may be effective at lowering the risk of esophageal cancer. Researchers at Harvard Medical School and VA Boston Healthcare System found that EGCG effectively inhibited the growth and reproduction of esophageal cancer cells. It was found that EGCG induced “cell suicide,” preventing the cancerous cells from replicating. In addition, increased EGCG concentration led to a higher rate of cell suicide, with no harm to healthy cells.

In recent studies, green tea extract (standardized to 90 mg of EGCG) increased the 24-hour energy expenditure in human subjects, thus aiding in weight reduction. Plus, the antioxidants of green tea are also beneficial for the heart, as they help decrease levels of LDL ("bad") cholesterol. In addition, green tea contains a small amount of caffeine (1% or 5 mg), so it serves as a mild appetite suppressant.

NSI Green Tea Extract (standardized 98% polyphenols, 80% catechins and 45% EGCG) (leaves) 500 mg

Get full-potency Green Tea Extract $19.95 from Vitacost

The anti-carcinogenic activity of green tea catechins

Green Tea - (camellia sinensis)

Cancer Research. 2005 March 15;65(6):2059-64.

A naturally occurring gallated polyphenols isolated from green tea leaves, (-)-epigallocatechin gallate (EGCG), has been shown to be an inhibitor of dihydrofolate reductase (DHFR) activity in vitro at concentrations found in the serum and tissues of green tea drinkers (0.1-1.0 micromol/L). These data provide the first evidence that the prophylactic effect of green tea drinking on certain forms of cancer, suggested by epidemiologic studies, is due to the inhibition of DHFR by EGCG and could also explain why tea extracts have been traditionally used in "alternative medicine" as anticarcinogenic/antibiotic agents or in the treatment of conditions such as psoriasis.

Nutraceutical Research

Chemopreventive effect of green tea (Camellia sinensis) against cigarette smoke-induced mutations (SCE) in humans.

J Cell Biochem Suppl, 130():68-75 1997

Green tea (Camellia sinensis) is consumed daily between the meals or after meals in Japan and other Asian countries. In recent years, green tea and its major polyphenolics have been demonstrated to prevent chemically induced tumors in a variety of experimental animal models system. The exact mechanism(s) of its anticarcinogenic activity remains to be elucidated, but green tea polyphenolics have demonstrated antimutagenic, anticarcinogenic, antioxidant, and antipromotional effects, including inhibition of Phase I and inducing Phase II enzymes. Enzyme activities of glutathione peroxidase, catalase, and quinone reductase, and glutathione S-transferase are also induced. However, a paucity of green tea effects in humans prompted us to investigate antimutagenic effects of green tea against smoke-induced mutation in humans. Chemopreventive effects of green tea and coffee among cigarette smokers were examined in 52 clinically healthy male subjects between 20-51 years of age. Blood specimens were obtained from non-smokers (Group I), smokers (II), smokers consuming green tea (III), and smoker/coffee drinkers (IV). The mean years of cigarette smoking ( 10 cigarettes/day) of Groups II, III, and IV ranged from 13.4-14.7 years. Daily intake of green tea and coffee was 3 cups/day/6 months (III and IV). The frequencies of sister-chromatid exchange (SCE) in mitogen-stimulated peripheral lymphocytes from each experimental group were determined and statistically analyzed. SCE rates were significantly elevated in smokers (9.46 +/- 0.46) vs. non-smokers (7.03 +/- 0.33); however, the frequency of SCE in smokers who consumed green tea (7.94 +/- 0.31) was comparable to that of non-smokers, implying that green tea can block the cigarette-induced increase in SCE frequency. Coffee, by contrast, did not exhibit a significant inhibitory effect on smoking-induced SCE.

Learn more about the effects of Green Tea Polyphenols

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