Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. In recent years it has become popular in Europe and North America and now green tea pills are touted for weight loss, as potent antioxidants, and for tumor prevention.
Potential health benefit
Human research is still very early, but the potential health benefits ascribed to green tea include antioxidant effects, cancer chemoprevention, antiviral effects, blood thinning properties, improving cardiovascular health, slowing mental decline, enhancing weight loss, arthritis protection, and protecting the skin from the damage caused by ionizing radiation. The compound EGCG found in green tea has been shown to regulate dozens of disease-specific molecular targets. Long term human research is required before we determine the appropriate dosage and amount of green tea or green tea extract required to provide these health benefits. However more is not better since high amounts of consumption can lead to sleep disturbances which are harmful to optimal health.
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Extract, 100 mg, yielding 35 mg EGCG
Green Tea Extract offers a convenient way to get the benefits of green tea in a highly concentrated pill form. This product is standardized for bioflavonoid-like antioxidants known as polyphenols, particularly epigallocatechin gallate which has been found in scientific studies to be a potent antioxidant.
Green Tea Extract Yielding 35 mg epigallocatechin gallate
Suggested Use: 1 green tea extract tablet two or three times a week with breakfast or lunch. Take the pill in the morning or midday before or with a meal. Evening use may lead to mild insomnia. There is some early anecdotal reports that taking high amounts of GTE which contain catechins can cause some harm to the liver. For this reason I suggest taking no more than one pill three times a week.
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Tea information and consumption
Tea is the most widely consumed beverage aside from water. Green tea contains polyphenolic compounds, which account for 30% of the dry weight of the leaves. Most of the polyphenols are flavanols, of which epigallocatechin-3-gallate is the most abundant. Tea is manufactured in three basic forms:
Black Tea -- During production, oxidation is promoted so
that most of these substances are oxidized.
Green tea is prepared in such a way as to prevent the oxidation of green leaf polyphenols.
Oolong tea is a partially oxidized product. Of the approximately 3 million metric tons of dried tea manufactured, only 20% is green tea and less than 2% is oolong tea.
What's in green tea?
The fresh leaf is unusually rich in polyphenols which may constitute up to 30% of the dry leaf weight. Polyphenols include catechins, flavanols, chlorogenic acid, epigallocatechin gallate (EGCG), and one unique to tea, theogallin. Caffeine in green tea is present at an average level of 3% along with very small amounts of methylxanthines, theobromine and theophylline. The amino acid theanine (5-N-ethylglutamine) is also unique to tea.
Tea and Weight Loss Diet, a fat burner?
Human studies regarding the benefit of green tea in weight loss have not shown consistent results. In one study mentioned below, daily consumption of green tea for 12 weeks reduced body fat. Green tea could enhance metabolism. Scientists are still evaluating whether a green tea pill by itself leads to weight loss. See below for more green tea and weight loss research information. If you plan to drink green tea for weight loss, avoid drinking after mid afternoon or early evening so that your sleep is not disturbed.
effects of green tea: from bedside to bench.
Mol Nutr Food Res. 2006.
Green tea, green tea catechins, and epigallocatechin gallate have been demonstrated in cell culture and animal models of obesity to reduce adipocyte differentiation and proliferation, lipogenesis, fat mass, body weight, fat absorption, plasma levels of triglycerides, free fatty acids, cholesterol, glucose, insulin and leptin, as well as to increase beta-oxidation and thermogenesis. Adipose tissue, liver, intestine, and skeletal muscle are target organs of green tea, mediating its anti-obesity effects. Studies conducted with human subjects report reduced body weight and body fat, as well as increased fat oxidation and thermogenesis and thereby confirm findings in cell culture systems and animal models of obesity. There is still a need for well-designed and controlled clinical studies to validate the existing and encouraging human studies.
Ingestion of a tea rich in catechins leads
to a reduction in body fat and malondialdehyde-modified LDL in men.
American Journal of Clinical Nutrition, 2005
We investigated the effect of catechins from green tea on body fat reduction and the relation between oxidized LDL and body fat variables. Design: After a 2-wk diet run-in period, healthy Japanese men were divided into 2 groups with similar BMI and waist circumference distributions. A 12-wk double-blind study was performed in which the subjects ingested 1 bottle oolong tea /d containing 690 mg catechins (green tea extract group; n = 17) or 1 bottle oolong tea /d containing 22 mg catechins. Body weight, BMI, waist circumference, body fat mass, and subcutaneous fat area were significantly lower in the green tea extract group than in the control group. Conclusion: Daily consumption of green tea containing 690 mg catechins for 12 wk reduced body fat, which suggests that the ingestion of catechins from green tea might be useful in the prevention and improvement of lifestyle-related diseases, mainly obesity.
Effect of long-term oral administration of green tea extract on weight gain and
glucose tolerance in Zucker diabetic (ZDF) rats.
J Herb Pharmacother. 2005.
There have been some claims that green tea reduces weight and lowers blood glucose in diabetes. Intraperitoneal injections of green tea catechins in diabetic rats have shown beneficial effects. To determine if oral administration of green tea would prevent development of diabetes, young Zucker diabetic rats were dosed with green tea extract containing 50-125 mg/kg of Epigallocatechin gallate starting at 7 weeks of age, before the appearance of excessive weight gain and glucose elevation. While there was a trend toward lower weight gain and average daily glucose, there was no statistically significant difference.
Additional health benefits
Green tea has several potential health benefits that are slowly being discovered, here are some preliminary results:
An ingredient in green tea that researchers think might fight cancer may also protect the brain from the memory-destroying Alzheimer’s disease. Scientists injected mice with an antioxidant called epigallocatechin-3-gallate and said it decreased production of beta-amyloid, a protein that forms the plaques that clog the brains of Alzheimer’s victims.
Previous research had mentioned EGCG has protective effects against betaA-induced neuronal apoptosis (cell death) through scavenging reactive oxygen species, which may be beneficial for the prevention of Alzheimer's disease.
A higher consumption of green tea is associated with a lower prevalence of cognitive impairment.
Some green tea catechins are chondroprotective (protecting cartilage) in lab studies, and that consumption of green tea may benefit the arthritis patient by reducing inflammation and slowing cartilage breakdown. Further studies will be required to determine whether these compounds access the joint space in sufficient concentration and in a form capable of providing efficacy when ingested as tea or capsule.
Anti-platelet (blood thinning) activity of green tea catechins is mediated by inhibition of cytoplasmic calcium increase.
Drinking green tea may lessen the effects of the medication nadolol (Corgard), used to treat high blood pressure, Jan. 13, 2014, Clinical Pharmacology & Therapeutics, online.
There is growing evidence that drinking green tea may reduce the risk for various types of cancer. However, little is known regarding the cancer preventive benefit of green tea supplements and the appropriate dosage.
Researchers at the University of Murcia in Spain and the John Innes Cente in Norwich, England have shown that a compound called EGCG in green tea prevents cancer cells from growing by binding to a specific enzyme. They showed for the first time that EGCG, which is present in green tea at relatively high concentrations, inhibits the enzyme dihydrofolate reductase, which is a recognized, established target for anti-cancer drugs. Green tea has about five times as much EGCG as regular tea. Green tea has been suspected to decrease rates of certain cancers but scientists were not sure what compounds were involved or how they worked. Nor had they determined how much green tea a person would have to drink to have a beneficial effect. EGCG is probably just one of a number of anti-cancer mechanisms in green tea.
Epidemiological data have
suggested that EGCG may provide protective effects against hormone related
cancers, namely breast or prostate cancer.
Researchers at the University of Murcia in Spain and the John Innes Center in Norwich, England have shown that EGCG prevents cancer cells from growing by binding to a specific enzyme. They showed for the first time that it inhibits the enzyme dihydrofolate reductase, which is a recognized, established target for anti-cancer drugs. Green tea has about five times as much EGCG as regular tea. Green tea has been suspected to decrease rates of certain cancers but scientists were not sure what compounds were involved or how they worked. Nor had they determined how much green tea a person would have to drink to have a beneficial effect. EGCG is probably just one of a number of anti-cancer mechanisms in green tea. EGCG targets multiple MMP-mediated cellular events in cancer cells and provides a new mechanism for the anticancer properties of that molecule. Understanding the basic principles by which EGCG inhibits tumour invasion and angiogenesis may lead to the development of new therapeutic strategies, in addition to supporting the role of green tea as a cancer chemopreventive agent.
EGCG targets multiple MMP-mediated cellular events in cancer cells and provides a new mechanism for the anticancer properties of that molecule.
Herbal Green tea extract may interfere with a process that helps early bladder cancer to spread throughout the body. The findings bolster ongoing studies into green tea extract as a cancer treatment -- and may give green tea drinkers more reason to savor every cup. The investigators found that when they exposed human bladder cells to both a cancer-causing chemical and green tea extract, the extract interfered with a particular process by which early cancer cells become invasive and spread throughout body tissue.
Reduced breast cancer risk
Green tea may help treat a form of adulthood leukemia. Doctors at the Mayo Clinic in Rochester, Minnesota, found that of four patients who started drinking green tea or taking green tea extracts, three showed clear improvements in their condition in the following months. The patients all had chronic lymphocytic leukemia, or CLL, a form of leukemia that usually arises during or after middle-age and typically progresses slowly. Like all types of leukemia, CLL is a cancer of the blood and bone marrow, in which abnormal white blood cells replace healthy blood cells. A study showed that one compound found in green tea, known as EGCG, was able to kill cancer cells that were taken from CLL patients and put in a test tube with the tea compound. Leukemia Research, online December 1, 2005.
Early research suggests it may lower PSA levels.
Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from a one-year proof-of-principle study.
Cancer Res. 2006.
The purity and content of GTCs preparations were assessed by high-performance liquid chromatography epigallocathechin, 5%; epicatechin, 12%; epigallocatechin-3-gallate, 51%; epicatechin-3-gallate, 6%; total green tea catechins, 75%; caffeine, <1%]. Sixty volunteers with HG-PIN, who were made aware of the study details, agreed to sign an informed consent form and were enrolled in this double-blind, placebo-controlled study. Daily treatment consisted of three green tea catechin capsules, 200 mg each (total 600 mg/d). After 1 year, only one tumor was diagnosed among the 30 green tea catechins -treated men (incidence, approximately 3%), whereas nine cancers were found among the 30 placebo-treated men (incidence, 30%). Total prostate-specific antigen did not change significantly between the two arms, but green tea catechins -treated men showed values constantly lower with respect to placebo-treated ones. International Prostate Symptom Score and quality of life scores of green tea catechins -treated men with coexistent benign prostate hyperplasia improved, reaching statistical significance in the case of International Prostate Symptom Scores. No significant side effects or adverse effects were documented. To our knowledge, this is the first study showing that green tea catechins are safe and very effective for treating premalignant lesions before prostate cancer develops. As a secondary observation, administration of green tea catechins also reduced lower urinary tract symptoms, suggesting that these compounds might also be of help for treating the symptoms of benign prostate hyperplasia.
Japanese women, but not Japanese men, who regularly drink 5 or more cups daily appear about 20 percent less likely to develop stomach cancer. Gut, September 9, 2009.
Consumption of green tea is associated with lower serum concentration of total cholesterol in Japanese healthy workers age 40-69 years.
Flavanol epigallocatechin-3-gallate is shown to be a potent natural inhibitor of leukocyte elastase that may be used to reduce elastase-mediated progression to emphysema and tumor invasion.
Dr. Kaijun Niu, at Tohoku University Graduate School of Biomedical Engineering in Sendai, found men and women aged 70 and older who drank four or more, versus one or fewer, cups of green tea daily were less likely to have symptoms of depression. Dr. Kaijun Niu published the results of this study in the American Journal of Clinical Nutrition, 2009.
Epigallocatechin gallate supplementation alleviates diabetes in rodents.
J Nutr. 2006.
This study shows that EGCG beneficially modifies glucose and lipid metabolism in H4IIE cells and markedly enhances glucose tolerance in diabetic rodents. Dietary supplementation with EGCG could potentially contribute to nutritional strategies for the prevention and treatment of type 2 diabetes mellitus.
Japanese men who drink green tea on a regular basis have healthier gums. Journal of Periodontology, 2009.
High blood pressure
Drinkers of green tea and oolong tea are less likely to develop hypertension than nondrinkers.
Epigallocatechin-3-gallate has been suggested to have antiviral activity. To determine the effects of EGCG on HIV infection, peripheral blood lymphocytes infected with HIV were incubated with increasing concentrations and it strongly inhibited the replication of the HIV virus.
People who regularly drink green tea may have a lesser risk of mental decline as they grow older. A study of more than 1,000 Japanese adults in their 70s and beyond, found that the more green tea men and women drank, the lower their odds of having cognitive impairment. Older adults who drank two or more cups of green tea per day were about half as likely to show cognitive impairment as those who drank three cups or less each week. Men and women who averaged one cup per day fell somewhere in between.
Daily consumption of green tea catechin delays
memory regression in aged mice.
Because oxidative stress has been implicated in brain senescence, we investigated the effects of green tea catechin (GT-catechin), a potential antioxidant, in senescence-accelerated (SAMP10) mice. The mouse is a model of brain senescence with short life span, cerebral atrophy and cognitive dysfunction. Mice were fed water containing 0.02% GT-catechin from 1- to 15-month-old. The mean dose was about 35 mg/kg/day. We found that daily consumption of GT-catechin prevented memory regression and DNA oxidative damage in these mice. GT-catechin did not prolong the lifetime of SAMP10 mice, but it did delay brain senescence.
Does Green Tea Enhance Longevity?
According to a Japanese study, those who consumed the most green tea over an 11-year period were less likely to die from cardiovascular disease or any other cause, except cancer, than were the less-frequent green tea drinkers. However, because this was an observational study, the debate on the effects of green tea on heart disease and cancer is not over. Although laboratory and animal studies have shown that the polyphenols in green tea may be protective against cardiovascular disease and cancer, it is not clear if these findings extend to humans. Dr. Kuriyama and colleagues analyzed information on 40,530 Japanese adults, 40 to 79 years old, who participated in the Ohsaki National Health Insurance Cohort Study. The subjects, who were followed from 1995 to 2005, were from a northeastern region of the country where most of the adults drink green tea three or more times per day. Adults who drank the most green tea were the least likely to die from cardiovascular disease. Men who consumed at least five cups of green tea each day were 12 percent less likely to die from any cause. Whereas, women who drank five or more cups of green tea each day were 23 percent less likely to die from any cause and 31 percent less likely to die from cardiovascular disease.
Dr. Sahelian says: For the time being I prefer people drink a variety of herbal teas as opposed to predominantly one type of tea. Also, if you drink to many cups a day it will influence your sleep and if you don't get a deep rest at night it could have a negative impact on your health.
Green tea consumption and mortality due to
cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study.
Green tea polyphenols have been extensively studied as cardiovascular disease and cancer chemopreventive agents in vitro and in animal studies. However, the effects of green tea consumption in humans remain unclear. We investigated the associations between green tea consumption and all-cause and cause-specific mortality with the Ohsaki National Health Insurance Cohort Study, a population-based, prospective cohort study initiated in 1994 among 40,530 Japanese adults aged 40 to 79 years without history of stroke, coronary heart disease, or cancer at baseline. Participants were followed up for up to 11 years for all-cause mortality and for up to 7 years for cause-specific mortality. Over 11 years of follow-up (follow-up rate, 86%, 4209 participants died, and over 7 years of follow-up (follow-up rate, 89%), 892 participants died of cardiovascular disease and 1134 participants died of cancer. Green tea consumption is associated with reduced mortality due to all causes and due to cardiovascular disease but not with reduced mortality due to cancer.
Life Sci. 2013. Potential benefits of green tea polyphenol EGCG in the prevention and treatment of vascular inflammation in rheumatoid arthritis.
Green Tea Side effects, safety, risk
Green tea has caffeine and methylxanthines, so avoid drinking or taking the capsules in the evening. Even if you drink it in the morning and you are sensitive to herbal stimulation, you may find that it could interfere with deep sleep. If you have a tendency to have insomnia, avoid herbal teas and even decaf coffee. I have not come across any other common adverse reactions at this time except this one caution:
Caution: In rare cases extracts from green tea have been reported to adversely affect the liver. Discontinue use and consult a healthcare practitioner if you have a liver disorder or develop symptoms of liver trouble, such as abdominal pain, dark urine, or jaundice. If you plan to take it for prolonged periods, take a week off each month.
Green tea extract: a potential cause of acute liver failure.. World J Gastroenterol. August 2013.
Q. I have a concern about the recent decision to put
warning labels on supplements containing green tea extracts. it warns of
possible liver damage.
A. The study that found green tea extract polyphenols may damage liver tissue used high doses injected into small mammals. Many Japanese drink green tea several cups a day without problems. I am not concerned that taking a green tea supplement at one capsule or tablet a few times a week would cause any liver problems. As with any supplement, it is a good idea to take breaks from use. Low dosages of many supplements are often of benefit, but high dosages could be harmful.
Q. Although I am aware and have read on many websites that Green Tea has anti
cancer properties, i was alarmed to read today on a couple of websites that it
can actually cause Esophageal Cancer! This is what i read from the site as one
of the possible side effects: "Some people show hypersensitivity reactions with
green tea. Others develop the condition after long-term use characterized by
hives, swelling of ears, lips, tongue and face, difficulty breathing, closing of
the throat and skin irritation. Another grave side effect that can be caused by
heavy and long-term consumption is esophageal cancer. There are
agents that remain and accumulate in the esophageal area leading to the
development of cysts and tumors. Too much green tea can cause a variety of side
effects such as anxiety, insomnia, nervousness, irritability, mood swings,
interrupted sleep, cardiac arrhythmia, headache, heartburn, loss of appetite,
gastrointestinal upset, diarrhea and constipation. It can also interact with
other substances thereby causing problems. Do not drink tea if you're taking
blood thinners like warfarin or Coumadin or it might cause hemorrhage or
Herbal teas in general have been suggested to be contributory to the development
of cancer. There seem to be carcinogenic effects that come with chronic use.
Teas high in tannin may lead to iron deficiency and microcytic anemia. Other
associated effects are liver and kidney failure and bronchial and respiratory
This concerns me as i have been taking green tea for a few years now and just recently have been taking about 4 capsules a day, each one at 300mg (polyphenols 95% & EGCG 40%) Is this to much to be taken daily?
A. Too much of a good thing is not so good. Esophageal cancer is quite rare and is not a major concern. Most long term epidemiological studies have shown benefits from drinking green tea and Asians who drink a lot of this tea do not show any noticeable harm. However, it is a good idea to be reasonable in one's consumption of this product either in tea form or in pills, and it is also a good idea to take occasional breaks.
There are countless green tea products, including bags, capsules, tablets, powder, green tea gum, combinations with other supplements and organic. Green tea is sold by raw material suppliers in different extracts, ranging from 30%-95%, standardized to green tea catechins.
Q. Will drinking a lot of green tea cause free estrogen to go up in the body (due to the phytoestrogens)? If so, could this potentially make someone estrogen dominant?
A. Not likely. Phytoestrogens have both estrogen agonist and estrogen antagonist activity in different tissues. They don't work the same way as regular estrogen hormone.
Q. Can this supplement be used together with another anti
cancer agent called DIM?
A. Probably as long as the dosages are reasonable, see diindolemethane dim for additional research studies.
Q. A friend
of mine yesterday said she read that if you drink green tea with cow's
milk that it will completely destroy the antioxidant properties. Do you know if this is true?
A. We have no indications at this time that drinking green tea with milk destroys its benefits to a significant extent.
Q. Is green tea okay to
drink during pregnancy? Is it good for nausea during pregnancy.
A. I can't foresee a cup a day to pose any problems during pregnancy. I don't think it helps relieve nausea.
Q. I am trying my best to lose weight, but am
unfortunately not noticing any difference. I eat healthy food and do
exercise, so I am considering taking a green tea tablet to try and burn
fat. I read off a bottle of green tea tablets that you should consult with
your physician if you are on medications before starting the tablets. I
have minor epilepsy and take three medications to keep it under control. I
take Keppra, Tegretol XR and Lamictal everyday morning and night. Can I
take green tea tablets as well, without any side effects from my epilepsy
A. Green tea tablets are unlikely to cause weight loss by themselves. Anyone with a seizure disorder needs to be careful taking herbs, especially those that have a stimulating nature.
Q. Do any doctors advocate that people take green tea supplements for their antioxidant and other benefits? If so, what's the amount of green tea they -- or that you -- advise taking daily? I find studies showing green tea benefits this or that, but I can't find anyone who actually suggests a daily amount.
A. There is no single answer since there are many factors that are involved in green tea dosage including age, medical condition, other supplements taken, other medicines used, activity level, whether they drink coffee or tea and how much, sleep patterns, etc. Also it depends on the extract potency, the quality of the green tea, etc.
Q. If I drink a lot of green tea will it flush
out the good stuff in my body and mess up my electrolytes? I was told that
if I drink green tea all day or a lot of it then it isn't good for me.
A. As a general rule, it is not a good idea to drink or eat too much of the same fluid or food. Too much green tea could cause alertness and interfere with sleep since green tea has caffeine and other methyl-xanthines such as theobromine which cause shallow sleep if ingested in the evening. It is a good idea to drink a variety of different herbal teas, not just exclusively green tea.
Q. I have bought most of your excellent soft
cover booklets over the years, and always read carefully your materials
when they come up in my research engine etc. I'm a daily user of fresh
juice extractor drinks plus nutraceuticals (capsule powers) I add to them,
for health, fitness, metabolism controls and nootropic purposes going
toward the alkaline level etc. I've read your data on green tea...and
while I've begun doing it recently...my question is. Is it okay to add the
contents of a quality green tea
bag to my drinks as a powder for supplementary purposes. How far removed
is an extract from the green tea bag powder - As you know a really good
supplemented nutritional program can be quite expensive. So if this green
tea bag content has no bad side effects, I would like to continue this
A. I don't see any reason why the green tea bag contents cannot be used. Over time, use different green tea bags from different sources.