Green tea is consumed primarily in China, Japan, and a few countries in North Africa and the Middle East. In many Japanese or Chinese restaurants, one of the dessert options is green tea ice cream. 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 by many who practice alternative medicine. What does the research say about the benefits of such pills? Do supplements help with weight loss and are they an effective diet aid?
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What's in green tea herb?
Fresh green tea 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.

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 and fat burner, arthritis protection, and protecting the skin from the damage caused by ionizing radiation. The compound EGCG found in green tea extract 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.

Green tea and weight loss diet - a fat burner?
Green tea consumption is reportedly associated with various health-promoting properties. For example, it has been shown to promote fat oxidation in humans at rest and to prevent obesity and improve insulin sensitivity in mice.
   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 but another study did not show weight loss with the use of green tea extract supplements. 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. It is quite possible that the combination of green tea extract and other supplements that influence appetite or metabolism could lead to weight loss.

Effect of green tea extract on obese women: a randomized, double-blind, placebo-controlled clinical trial.
Clin Nutr. 2008. Community Medicine Research Center, National Yang-Ming University, Taipei, Taiwan.
Seventy-eight of 100 obese women aged between 16 and 60 years with BMI>27 kg/m(2) and who had not received any other weight control maneuvers within the last 3 months completed this study. The subjects were randomly divided into Groups A and B. Group A received green tea extract while Group B took cellulose as a placebo, one capsule (400mg) three times each day for 12 weeks. The body weight (BW), body mass index (BMI) and waist circumflex (WC) were measured at the beginning of the study and after 12 weeks of treatment with green tea extract. There was only a 0.3% reduction in BW after 12 weeks of treatment with green tea extract. There was no statistical difference in % reduction in BW, BMI and WC between the green tea extract and placebo groups. Within group comparison revealed that the green tea extract group had significant reduction in LDL-cholesterol and triglyceride, and marked increase in the level of HDL-cholesterol, adiponectin and ghrelin. On the other hand, the placebo group showed significant reduction in triglyceride only, and a marked increase in the level of ghrelin alone. This study showed no statistical difference in % reduction in BW, BMI and WC between the green tea extract and placebo groups after 12 weeks of treatment. The intake of green tea extract (491 mg catechins containing 302 mg EGCG) for 12 weeks is considered safe.

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
Catechins, the major component of green tea extract, have various physiologic effects. There are few studies, however, on the effects of catechins on body fat reduction in humans. 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 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. 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.

Anti-obesity effects of green tea: from bedside to bench.
Mol Nutr Food Res. 2006.
Green tea, green tea catechins, epicatechin, and epigallocatechin gallate (EGCG) 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.

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 (EGCG) 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.

FDA warning 2010
The FDA has issued two warning letters related to claims made for green tea products. One ordered Unilever Americas to stop claiming that its Lipton Green Tea 100% Naturally Caffeinated product has a significant cholesterol-lowering effect and is "a naturally rich source of antioxidants." The other ordered Cadbury Adams USA to stop claiming that its Canada Dry Sparkling Green Tea Ginger Ale was "enhanced with 200 mg of antioxidants from green tea and vitamin C."

Best green tea diet supplement
There are a number of green tea diet supplements on the market, and since no studies have been done comparing all of them, it is impossible to say honestly which one of these products is the best green tea diet supplement.

Health benefits
Green tea has several potential health benefits that are slowly being discovered, here are some preliminary results:

Alzheimer's disease
A 50 percent pure extraction of EGCG - a flavonoid which is the most potent of four major catechins in green tea, was examined by Dr. Stephane Bastianetto at the Douglas Mental Health University Institute, McGill University in Montreal. In the study, rats were fed food that contained Teawell 50, compared to a control group whose food did not contain the extract. Results showed that rats who ate Teawell 50 had an 18 percent reduction of free radicals in a key region of the brain involved with learning and memory. This region is severely damaged when Alzheimer's is present. "This suggests regular consumption of green tea may protect against the deleterious effects of oxidative stress, delaying or preventing age-related memory deficits," said Dr. Bastianetto. According to Dr. Stephane Bastianetto, discovering Teawell 50's ability to cross the blood-brain barrier in sufficient concentrations and actually reach the brain is significant." Green tea has higher concentrations of beneficial catechins - especially EGCG," said Christine Renken of A. Holliday & Company. "Extracting this substance allows it to be used in foods such as yogurt and beverages as well as supplements, pet foods and even beauty products." Studies have shown that EGCG may inhibit production of inflammatory molecules associated with rheumatoid arthritis; enhance the immune system, boost metabolism and burn fat as well as protecting against gum disease and reducing cavities. Based in Toronto, Canada, since 1975 A. Holliday & Company Inc. has been a major distributor of coffee and tea products. A. Holliday & Company products are used with many well known international brands and private label products from food and beverage, to baking and dairy, to flavour and ingredient manufacturers, to pharmaceuticals and cosmetics.

Anti aging benefit of drinking green tea
According to a study done with Japanese adults, those who consumed the most green tea were less likely to die from cardiovascular disease or any other cause, except cancer, than were the less-frequent green tea drinkers. 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 an 11 year period, 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 were the least likely to die from cardiovascular disease. Men who consumed at least five cups each day were 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.   
   Comments: For the time being, if you don't drink green tea, it may be a good idea to have a cup a day or a few times a week. If you already drink it on a daily basis, you could perhaps add another cup a day. It's also possible that drinking a variety of teas may provide more benefit than just drinking additional green tea. Who's to say other herbal teas (and there are so many to choose from) are not as healthy? Another option is to take a green tea extract supplement a few times a week. Avoid the use of the tea or the supplement after mid afternoon since the caffeine and stimulants may interfere with sleep. One factor to consider is that this study was done in Japan. Americans have a different diet and lifestyle. Will the results be similar in those on a Western diet?

Antioxidant
Green tea extract capsules, when given to humans, increase the production of such as glutathione S-transferase (GST) enzymes which are helpful in detoxification and cancer prevention. Dr. H.-H. Sherry Chow, of the University of Arizona, Tucson, gave volunteers four green tea extract capsules, each containing 200 mg of epigallocatechin gallate, every morning prior to eating. This provided the equivalent amount of epigallocatechin gallate obtained from drinking 8 to 16 cups of green tea daily. Those with the lowest GST levels at the start of the study and who took the green tea extracts were found to have glutathione S-transferase enzymes increased by 80 percent. Those who had good levels of glutathione S-transferase did not have much of a change in their levels. Cancer Epidemiology, Biomarkers and Prevention, 2007.

Anti viral activity
Epigallocatechin-3-gallate has been suggested to have antiviral activity. To determine the effects on HIV infection, peripheral blood lymphocytes infected with HIV were incubated with increasing concentrations. EGCG strongly inhibited the replication of the HIV virus.

Anti platelet activity
Anti-platelet (blood thinning) benefit of green tea catechins is mediated by inhibition of cytoplasmic calcium increase.

Green tea extract for arthritis and healthy joints
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.

Cancer prevention
Several compounds in green tea have anti cancer potential, including against prostate cancer.

   Pancreatic cancer -  In mouse studies, green tea extract EGCG inhibits pancreatic cancer growth, invasion, metastasis and angiogenesis. Human studies will elucidate whether green tea extract could be used for the management of pancreatic cancer prevention and treatment.

Diabetes and blood sugar
Drinking green tea or taking a supplements does not seem to have a major role to play in lowering blood sugar, but the antioxidant effects are nevertheless beneficial for those with diabetes. Green tea may reduce advanced glycation end products and reduce the rate of collagen cross linking. It does not appear that it has much of an influence on blood sugar levels. However, this does not mean it is not beneficial to those with diabetes. Since it has has potent polyphenol antioxidants, drinking it or taking an extract may be helpful in terms of overall antioxidant status in the body. However, green tea extract may reduce collagen cross linking which is often a consequence of high blood sugar levels.

Heart health
Green tea has preventive effects on both chronic inflammatory diseases and lifestyle-related diseases including cardiovascular disease.
   Drinking green tea can protect heart arteries by keeping them flexible and relaxed, and therefore better able to withstand constant changes in blood pressure. Dr. Nikolaos Alexopoulos of Athens Medical School in Greece, reports that among 14 subjects, those who drank green tea showed greater dilation of their heart arteries on ultrasound 30 min. later than those drinking either diluted caffeine or hot water. Green tea flavonoids works on the lining of blood vessels, helping cells there to secrete the substances needed to relax the vessels and allow blood to flow more freely. These flavonoids act as antioxidants and help prevent inflammation in body tissue, that keep the vessels pliable. Flavonoids also protect against the formation of clots, which are the primary cause of heart attacks.

Healthy gums
Among middle-aged Japanese, the odds of having gum disease declines as the men's intake of green tea rises. For each daily cup they drink, the risk of having signs of gum disease -- including receding, easily bleeding gums -- is lowered. Dr. Yoshihiro Shimazaki, at Kyushu University in Fukuoka, Japan, examined 940 men between the ages of 49 and 59 for signs of gum disease. The odds of gum disease declined as green tea intake climbed, even with the other lifestyle factors considered. Journal of Periodontology, March 2009.

Exercise and athletic performance
The effects of EGCG on fat oxidation and endurance performance in male cyclists.
Int J Sport Nutr Exerc Metab. 2009. School of Sport and Exercise Science, Waikato Institute of Technology, Hamilton, New Zealand.
Green-tea extract (epigallocatechin-3-gallate; EGCG) has been shown to improve endurance capacity in mice. If a green-tea extract can stimulate fat oxidation and as a result spare glycogen stores, then athletes may benefit through improved endurance performance. Eight male cyclists completed a study incorporating a 3-way crossover, randomized, placebo-controlled, double-blinded, diet-controlled research design. All participants received 3 different treatments (placebo 270 mg, EGCG 270 mg, and placebo 270 mg + caffeine 3 mg/kg) over a 6-day period and 1 hr before exercise testing. It was concluded that green-tea extract offers no additional benefit to cyclists over and above those achieved by using caffeine.

Lung health
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.

More information
Tea is the most widely consumed beverage aside from water. It contains polyphenolic compounds, which account for 30% of the dry weight of the leaves. Most of the polyphenols are flavanols, of which EGCG is the most abundant. Tea is manufactured in three basic forms:

Black Tea -- During black tea 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.

Caffeine content
There are hundreds of types of green tea and countless green tea growing farms. Each batch will have a slightly different caffeine amount. In addition to caffeine, green tea has beneficial compounds mostly of the polyphenol class. A study done in Portugal evaluating various types of green tea found the caffeine content in green tea ranged between 140 to 340 mg per liter.

Green Tea side effects, safety, danger
A common green tea side effect is shallow sleep. Green tea has caffeine and methylxanthines, so avoid drinking or taking the capsules in the evening. We have not come across any other common green tea side effects 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 green tea extract for prolonged periods, take a week off each month.

I have a question about the recent decision to put warning labels on supplements containing green tea extracts. it warns of possible liver damage. Are there supplements derived from green tea extracts which will not be easily identifiable by their labels?
   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. We are not concerned that taking a green tea supplement at one capsule or tablet a few times a week would cause any liver problems.

Q. I read an article that made several claims regarding the benefits of green tea and extract. The article claims it cuts the risk for cancer due to the polyphenol antioxidants. It claims it reduces blood pressure by keeping blood vessels dilated. It says it helps memory and reduces the risk for Alzheimer's and Parkinson's disease.
   A. Laboratory studies have shown green tea has anti cancer potential, whether long term human studies will confirm this finding has yet to be determined. Green tea may have a slight benefit for blood pressure unless perhaps used in high amounts. Compounds in green tea may protect brain cells but it is too early to tell if drinking green tea or taking green tea extract supplements prevent or treat Alzheimer's disease or Parkinson's disease. Green tea extract may have slight thermogenic activity and may have some appetite suppressing activity that could lead to a slight weight loss.

Hepatotoxicity from green tea: a review of the literature and two unpublished cases.
Eur J Clin Pharmacol. 2009. Department of Physiology and Pharmacology, Sapienza, University of Rome, Rome, Italy.
To review the current literature on suspected green tea-related hepatic reactions and to describe two new cases reported within the framework of the Italian surveillance system of natural health products. A literature search of publication between 1999 and October 2008 retrieved 34 cases of hepatitis. Histological examination of the liver revealed inflammatory reactions, cholestasis, occasional steatosis, and necrosis. A positive dechallenge was reported in 29 cases. There was one reported death. A positive rechallenge occurred in seven cases (20%). In the two new cases, the causality assessment was judged as "possible" according to the RUCAM score. Our analysis of the published case reports suggests a causal association between green tea and liver damage. The hepatotoxicity is probably due to (-)-epigallocatechin gallate or its metabolites which, under particular conditions related to the patient's metabolism, can induce oxidative stress in the liver. In a few cases, toxicity related to concomitant medications could also be involved.

Safety of green tea extracts : a systematic review by the US Pharmacopeia.
Drug Saf. 2008. US Pharmacopeia, Rockville, Maryland, USA.
Recently, regulatory agencies in France and Spain suspended market authorization of a weight-loss product containing green tea extract because of hepatotoxicity concerns. This was followed by publication of adverse event case reports involving green tea products. In response, the US Pharmacopeia (USP) Dietary Supplement Information Expert Committee (DSI EC) systematically reviewed the safety information for green tea products in order to re-evaluate the current safety class to which these products are assigned. DSI EC searched PubMed (January 1966-June 2007) and EMBASE (January 1988-June 2007) for clinical case reports and animal pharmacological or toxicological information. Reports were also obtained from a diverse range of other sources, including published reviews, the US FDA MedWatch programme, USP's MEDMARX adverse event reporting system, the Australian Therapeutic Goods Administration, the UK Medicines and Healthcare products Regulatory Agency, and Health Canada's Canadian Adverse Drug Reaction Monitoring Program. Case reports pertaining to liver damage were evaluated according to the Naranjo causality algorithm scale. In addition, the Committee analysed information concerning historical use, regulatory status, and current extent of use of green tea products. A total of 216 case reports on green tea products were analysed, including 34 reports concerning liver damage. Twenty-seven reports pertaining to liver damage were categorized as possible causality and seven as probable causality. Clinical pharmacokinetic and animal toxicological information indicated that consumption of green tea concentrated extracts on an empty stomach is more likely to lead to adverse effects than consumption in the fed state. Based on this safety review, the DSI EC determined that when dietary supplement products containing green tea extracts are used and formulated appropriately the Committee is unaware of significant safety issues that would prohibit monograph development, provided a caution statement is included in the labelling section. Following this decision, USP's DSI ECs may develop monographs for green tea extracts, and USP may offer its verification programmes related to that dietary ingredient.

Questions
Q. I see supplements of EGCG being sold in high dosages. Are these safe to take?
   A. Consumers are switching from regular tea to green tea and other herbal teas. We are not big fans of taking large doses of isolated substances from herbs, such as a high amount of EGCG, preferring to take the whole powder or a less concentrated extract. Many people think the higher the dose of a substance they supplement, the healthier they will be, but that may not always be the case, and often is not the case. So, for the time being, we don't see the need to take a high dose of EGCG unless perhaps under medically supervised treatment for a health condition.

Q. Can you possibly tell me how many mg of caffeine would be in 50 mg of green tea (leaf) extract?
   A. This is impossible to say accurately since there are countless extract potencies of green tea and countless varieties of green tea leaf and herb. The level of caffeine could vary significantly between different extracts, growers, processors, and manufacturers.

Q. In regards to the green tea issue: I had been drinking 2 to 4 cups of green tea for about ten years, mostly organic
and de-caf. Last year I found out about the fluoride issue and also found out that green tea contains fluoride. During this time I was also drinking bottled water (I was concerned about possible lead in the water) and eating a good diet, mostly organic. I had no major health problems, just annoying sinus problems which would turn into infections several times/year. I did however have a lowered white cell count during this time (3.8-4.2) Then I developed sleep problems about 3 years ago and tried just about everything for them. I gave up drinking green tea last year (still have a cup of coffee with caffeine). Not only have my sleep problems ceased, but my white cell count is back to normal. I still can't believe the results but I still won't go back to drinking green tea. I did the research and I must be sensitive
to fluoride.
   A. Green tea, even decaf, has many compounds in it, such as catechins, that cause alertness. Drinking two to four cups of green tea a day will likely cause shallow sleep and at this time we are not convinced that it is the fluoride causing it.

Q. I am primarily concerned with cancer-induction characteristics, basically, about two substances: Tannins: there are studies out there showing that tanmins are carcinogenic, but the studies done in animals are a tad extreme, such as skin-tainting uv-exposing. Incidental information from Chine would suggest drinking a lot of tea is linked with stomach cancer. Green teas do contain a sizeable amount of tannins. What are the implications? Fluoride: there have been a few articles exposing fluorosis due to "brick tea" (i.e. low quality tea) and a few others measuring fluoride content of teas. As you may know, the tea plant is a fluoride concentrator. This means, that if it is watered with high fluoride content water, it will soak it and then release it in the tea. Personally (as a chemist) I believe that the only safe fluoride level in food is zero. From the articles I have seen, some green teas are down horrible fluoride-wise. They can release up to 4 or more times the "safe" (SIC) level of fluoride the water is allow to have. green tea extracts do not indicate fluoride content, and very few manufacturers provide this info, strictly upon request. It gets worst. Teas made from young leafs "should" have less fluoride, but the Oolong teas (for example) are as bad as regular tea. Would you still recommend green tea in this circumstances?
   A. Studies in Asia link green tea consumption to longevity. We are not concerned about drinking green tea a few times a week or a few times a month. If one analyzes in detail all the foods we eat, there is always something to worry about in just about every food. It's best not to worry excessively. The worry alone is more likely to be harmful to the body and mind than the actual minor toxins or other substances in the foods we eat or teas we drink.

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