Green Tea
Uses
Parts Used & Where Grown
All teas (green, black, and oolong) are derived from the same plant, Camellia sinensis. The difference is in how the plucked leaves are prepared. Green tea, unlike black and oolong tea, is not fermented, so the active constituents remain unaltered in the herb. The leaves of the tea plant are used both as a social and a medicinal beverage.
Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.
For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.
3 StarsReliable and relatively consistent scientific data showing a substantial health benefit.
2 StarsContradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1 StarFor an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.
This supplement has been used in connection with the following health conditions:
| Used for | Why |
|---|---|
3 Stars High Cholesterol green tea extract providing 107–856 mg of EGCG daily in smaller divided doses and with food | Green tea has been shown to lower total and LDL-cholesterol levels and improve cardiovascular health. Though uncommon, liver injury can occur with long-term use of green tea extract or EGCG. has been shown to lower total and LDL-cholesterol levels in a number of randomized controlled trials. Some research further shows green tea can lower blood pressure, promote weight loss, and reduce the risk of cardiovascular events. Its benefits on heart health have largely been attributed to its polyphenols, including catechins such as epigallocatechin gallate (EGCG). A meta-analysis of results from 31 randomized controlled trials with a combined total of 3,216 subjects found green tea supplementation reduced total and LDL-cholesterol levels. In other large meta-analyses, green tea extract was found to reduce total cholesterol levels, as well as triglyceride levels, in type 2 diabetics, and decrease total and LDL-cholesterol levels in individuals with overweight and obesity. A research review indicated green tea extract providing 107–856 mg of EGCG could induce significant reductions in LDL-cholesterol levels. EGCG, with its powerful antioxidant and anti-inflammatory effects, has also been linked to reduced risks of atherosclerosis and heart attack. |
3 Stars Metabolic Syndrome 600 to 900 mg of tea catechins daily | Strong evidence indicates green tea and black tea extracts can help individuals with metabolic syndrome reduce body weight, lower blood glucose levels, and raise HDL-cholesterol levels. Drinking tea has been associated with lower risk of metabolic syndrome, and both green and black tea extracts, as well as the green tea catechin epigallocatechin gallate (EGCG), have demonstrated positive effects in people with metabolic syndrome. One meta-analysis of six randomized controlled trials involving people with obesity and metabolic syndrome concluded consuming a green tea catechin-rich beverage reduces abdominal fat accumulation and improves metabolic status. A large meta-analysis of studies pooled findings from 16 controlled trials with a combined total of 1,090 participants with obesity and metabolic syndrome. The results showed that, while the evidence for green tea extract is stronger than that for black, both green and black tea extracts help lower blood glucose levels, raise HDL (“good”)-cholesterol levels, and reduce body mass index, but have no impact on blood pressure, triglycerides, or other cholesterol levels. Most studies finding beneficial metabolic effects used 600–900 mg of tea catechins per day for at least 12 weeks. It is important to note liver toxicity has been associated with the use of very high doses of green tea extracts. |
3 Stars Obesity An extract supplying 100–460 mg of EGCG per day | Green tea extract rich in polyphenols may support a weight-loss program by increasing energy expenditure and fat burning. Green tea contains caffeine and polyphenols known as catechins (such as epigallocatechin gallate, or EGCG), which may work synergistically to support weight loss. Meta-analyses and reviews of multiple randomized controlled trials have found green tea extract has a small positive effect on weight loss and fat loss in people with overweight and obesity. Research shows green tea extracts can inhibit carbohydrate- and fat-digesting enzymes, improve gut microbiome balance, activate normal adipose tissue metabolism, and possibly raise energy expenditure by increasing heat production. |
2 Stars Abnormal Pap Smear Twice weekly, apply a cream with 15% polyphenols to the cervix and/or take a 200 mg EGCG supplement daily | A preliminary study found that cervical dysplasia improved following treatment with epigallocatechin-3-gallate, a green tea flavonoid, for 8 to 12 weeks. In a preliminary study, women with cervical dysplasia were randomly assigned to receive either 200 mg per day of EGCG—a extract known as (-)-epigallocatechin-3-gallate—200 mg per day of poly E (another green tea extract), or no treatment (control group) for 8 to 12 weeks. More than 50% of the women receiving EGCG or poly E had an improvement in their Pap smear, compared with only 10% of the women in the control group. |
2 Stars Colon Cancer Drink a few cups per day | The polyphenols in green tea leaves may help protect against colon cancer. and black tea (Camellia sinensis) have both been studied to determine whether they cause or prevent cancer. The evidence on the protective effect of either type of tea is inconsistent. A number of preliminary studies have shown an association between drinking green tea and a reduced risk of some types of cancer, including colon cancer. In contrast, preliminary studies found that consumers of black tea do not appear to have a reduced risk of any type of cancer. |
2 Stars Down Syndrome Refer to label instructions | In double-blind studies of young adults with Down syndrome, supplementation with epigallocatechin-gallate (EGCG; a flavonoid present in green tea) significantly improved measures of cognitive function. In double-blind studies of young adults with Down syndrome, supplementation with epigallocatechin-gallate (EGCG; a flavonoid present in green tea) for 3-12 months significantly improved measures of cognitive function (episodic memory, visual recognition memory, inhibitory control, and adaptive behavior), compared with a placebo. The amount of EGCG given was 9 mg per 2.2 pounds of body weight per day. |
2 Stars Influenza Gargle with a liquid extract containing 200 mcg per ml three times per day | In one study, elderly nursing home residents in Japan who gargled with a green tea extract were less likely to get the flu than those who gargled without the green tea extract. In a preliminary study of elderly nursing home residents in Japan, only 1.3% of those who gargled with a three times a day during the winter developed influenza, whereas 10.4% of those who gargled without the green tea extract developed the disease (a statistically significant difference). The presumed active ingredients in the extract were a group of flavonoids called catechins, which were present in the extract at half the concentration as that in green tea. It is possible, therefore, that gargling with green tea itself might also be effective for preventing the flu. In a double-blind study of healthcare workers, the combination of 378 mg per day green tea catechins and 210 mg per day of theanine (another component of green tea) taken for 5 months reduced the incidence of influenza infection by 69%, when compared with a placebo. |
2 Stars Leukoplakia 3 grams daily of a combination of whole green tea, green tea polyphenols, and green tea pigments, along with painting the mixture on the lesions three times per day | A combination of whole green tea, green tea polyphenols, and green tea pigments painted on lesions may improve healing. In a double-blind trial, people with leukoplakia took 3 grams per day of a mixture of whole , green tea polyphenols, and green tea pigments orally and also painted the mixture of the tea on their lesions three times per day for six months. Those in the green tea group had significant improvement in the healing of their lesions. |
2 Stars Prostate Cancer Several cups per day (enough to provide 600 mg of catechins daily) | Drinking green tea or taking green tea catechins may help prevent prostate cancer in men at high risk of developing the disease. In a double-blind trial, men with precancerous changes in the prostate received a green tea extract providing 600 mg of catechins per day or a placebo for one year. After one year, prostate cancer had developed in 3.3% of the men receiving the green tea extract and in 30% of those given the placebo, a statistically significant difference. These results suggest that drinking green tea or taking green tea catechins may help prevent prostate cancer in men at high risk of developing the disease. |
2 Stars Sunburn Apply a formula containing 10% green tea polyphenols before sun exposure | Green tea contains polyphenols that have antioxidant and anti-inflammatory activity, and studies have suggested that these polyphenols can protect skin against ultraviolet rays. (Camellia sinensis) contains polyphenols that have antioxidant and anti-inflammatory activity, and animal and preliminary human studies have suggested that these polyphenols, when given orally or used topically, can protect skin against ultraviolet rays. In a small, controlled human study, topical application of green tea extracts containing from 2.5 to 10% polyphenols significantly reduced the amount of burning from exposure to ultraviolet rays, with the 10% solution exerting greater protective effect. |
2 Stars Type 2 Diabetes The best effective dose is unknown, but doses providing 450 mg of total green tea polyphenols (catechins) daily are considered moderate; doses providing 800 mg of EGCG or more daily have been linked to liver injury and are not considered safe. | Green tea may protect cardiovascular health and improve metabolism. Green tea is a rich source of antioxidant polyphenols called catechins, including the well-studied epigallocatechin gallate (EGCG). Through their anti-inflammatory and antioxidant effects, green tea catechins appear to protect cardiovascular health and improve metabolism in obesity, insulin resistance, and type 2 diabetes. Green tea consumption has been correlated with lower risk of type 2 diabetes and diabetes-related heart disease. In a preliminary trial, 400 mg per day of green tea extract standardized to contain 90% green tea polyphenols and 45% EGCG reduced arterial stiffness in subjects with type 2 diabetes. Although a meta-analysis of 17 randomized controlled trials, including a total of 1,133 subjects with various metabolic disorders, found that green tea consumption significantly improves blood glucose control and insulin sensitivity, another meta-analysis of six studies that only included participants with type 2 diabetes or pre-diabetes found no beneficial effects of green tea or green tea extract on insulin resistance or measures of glycemic control. Although an effective dose has not been identified, doses providing 800 mg of EGCG or more per day have been linked to liver injury and are not considered safe. |
1 Star Crohn’s Disease Refer to label instructions | Green tea is a tannin-containing herb that may be helpful to decrease diarrhea during acute flare-ups and has been used for this purpose in traditional medicine. Tannin-containing herbs may be helpful to decrease diarrhea during acute flare-ups and have been used for this purpose in traditional medicine. A preliminary trial using isolated tannins in the course of usual drug therapy for Crohn’s disease found them to be more effective for reducing diarrhea than was no additional treatment. Tannin-containing herbs of potential benefit include agrimony (Agrimonia spp.), , oak, witch hazel, and cranesbill. Use of such herbs should be discontinued before the diarrhea is completely resolved; otherwise the disease may be aggravated. |
1 Star Hemochromatosis Refer to label instructions | High-tannin tea has been shown to reduce the need for blood removal from people with iron overload, or hemochromatosis, in an open study. The tea had to be taken with meals and without lemon or milk to be effective. Tea is believed to help in hemochromatosis by preventing iron absorption. High-tannin tea has been shown to reduce the need for blood removal from people with iron overload, or hemochromatosis, in an open study. The tea had to be taken with meals and without lemon or milk to be effective. Tea is believed to help in hemochromatosis by preventing iron absorption. |
1 Star High Triglycerides Refer to label instructions | Drinking green tea may have a positive effect on triglyceride levels. Intake of three cups or less of daily has been shown not to affect blood triglyceride levels. Intake of four or more cups per day has been correlated with lower triglyceride levels. Overall, the evidence is unclear on how much of an effect high levels of intake of green tea has on triglyceride levels. |
1 Star Hives Refer to label instructions | Two components of green tea, the polyphenols epigallocatechin (EGC) and epicatechin gallate (ECG), are reported to have an antihistamine effect. Two components of , the polyphenols epigallocatechin (EGC) and epicatechin gallate (ECG), are reported to have an antihistamine effect. Some doctors recommend approximately 3 cups of green tea per day or about 3 grams of soluble components providing roughly 240 to 320 mg of polyphenols, although no human trials have studied the effects of green tea in people with hives. |
1 Star Immune Function Refer to label instructions | Green tea has stimulated production of immune cells and has shown anti-bacterial properties in some studies. has stimulated production of immune cells and has shown anti-bacterial properties in animal studies. More research is needed to evaluate the effectiveness of green tea in protecting against infection and other immune system-related diseases. |
1 Star Infection Refer to label instructions | Green tea is an herb that directly attack microbes. Herbs that directly attack microbes include the following: chaparral, eucalyptus, garlic, , lemon balm (antiviral), lomatium, myrrh, olive leaf, onion, oregano, pau d’arco (antifungal), rosemary, sage, sandalwood, St. John’s wort, tea tree oil, thyme, and usnea. |
1 Star Lung Cancer Refer to label instructions | Numerous preliminary studies have shown an association between drinking green tea and a reduced risk of several types of cancer including lung cancer. Numerous preliminary studies have shown an association between drinking and a reduced risk of several types of cancer including lung cancer. In contrast, preliminary studies of black tea consumption have not found that it protected against any type of cancer. |
Traditional Use (May Not Be Supported by Scientific Studies)
According to Chinese legend, tea was discovered accidentally by an emperor 4,000 years ago. Since then, Traditional Chinese Medicine has recommended green tea for headaches, body aches and pains, digestion, depression, immune enhancement, detoxification, as an energizer, and to prolong life.
How It Works
How It Works
Green tea contains volatile oils, vitamins, minerals, and caffeine, but the primary constituents of interest are the polyphenols, particularly the catechin called epigallocatechin gallate (EGCG). The polyphenols are believed to be responsible for most of green tea’s roles in promoting good health.1
Green tea has been shown to mildly lower total cholesterol levels and improve the cholesterol profile (decreasing LDL “bad” cholesterol and increasing HDL “good” cholesterol) in most,2, 3, 4, 5 but not all,6 studies. Green tea may also promote cardiovascular health by making platelets in the blood less sticky.
Green tea has been shown to protect against the oxidation of cholesterol to a more toxic molecule (oxidized cholesterol).7 Consumption of green tea increases antioxidant activity in the blood.8 Oxidative damage to LDL can promote atherosclerosis. While population studies have suggested that consumption of green tea is associated with protection against atherosclerosis,9 the evidence is still preliminary.
Several animal and test tube studies have demonstrated an anticancer effect of polyphenols from green tea.10, 11, 12 In one of these studies, a polyphenol called catechin from green tea effectively inhibited metastasis (uncontrolled spread) of melanoma (skin cancer) cells.13 The polyphenols in green tea have also been associated with reduced risk of several types of cancer in humans.14, 15, 16 However, some human studies have found no association between green tea consumption and decreased cancer risk.17, 18
In a double-blind trial, people with leukoplakia (a pre-cancerous oral condition) took 3 grams orally per day of a mixture of whole green tea, green tea polyphenols, and green tea pigments orally, and also painted a mixture of the tea on their lesions three times daily for six months.19 As compared to the placebo group, those in the green tea group had significant decreases in the pre-cancerous condition.
Compounds in green tea, as well as black tea, may reduce the risk of dental caries.20 Human volunteers rinsing with an alcohol extract of oolong tea leaves before bed each night for four days had significantly less plaque formation, but similar amounts of plaque-causing bacteria, compared to those with no treatment.21
Green tea polyphenols have been shown to stimulate the production of several immune system cells, and have topical antibacterial properties—even against the bacteria that cause dental plaque.22, 23, 24
One study found that intake of 10 cups or more of green tea per day improved blood test results, indicating protection against liver damage.25 Further studies are needed to determine if taking green tea helps those with liver diseases.
Tea flavonoids given by capsule reduced fecal odor and favorably altered the gut bacteria in elderly Japanese with feeding tubes living in nursing homes.26 The study was repeated in bedridden elderly not on feeding tubes, and green tea was again shown to improve their gut bacteria.27 These studies raise the possibility of using green tea in other settings where gut bacteria are disturbed, such as after taking antibiotics. Further studies are needed to clarify the role of green tea in this respect, however.
High-tannin tea has been shown to reduce the need for blood removal from people with iron overload, or hemochromatosis, in an open study.28 The tea had to be taken with meals and without lemon or milk to be effective. Tea is believed to help in hemochromatosis by preventing iron absorption.
In a double-blind trial, men with precancerous changes in the prostate received a green tea extract providing 600 mg of catechins per day or a placebo for one year. After one year, prostate cancer had developed in 3.3% of the men receiving the green tea extract and in 30% of those given the placebo, a statistically significant difference.29 These results suggest that drinking green tea or taking green tea catechins may help prevent prostate cancer in men at high risk of developing the disease.
There are four case reports in which certain types of leukemia or lymphoma (low grade B-cell malignancies) improved after the patients began taking green tea extracts.30
How to Use It
Much of the research documenting the health benefits of green tea is based on the amount of green tea typically consumed in Asian countries—about 3 cups (750 ml) per day (providing 240–320 mg of polyphenols).31 However, other research suggests as much as 10 cups (2,500 ml) per day is necessary to obtain noticeable benefits from green tea ingestion.32, 33 To brew green tea, 1 teaspoon (5 grams) of green tea leaves are combined with 1 cup (250 ml) of boiling water and steeped for three minutes. Decaffeinated tea is recommended to reduce the side effects associated with caffeine, including anxiety and insomnia. Tablets and capsules containing standardized extracts of polyphenols, particularly EGCG, are available. Some provide up to 97% polyphenol content—which is equivalent to drinking 4 cups (1,000 ml) of tea. Many of these standardized products are decaffeinated.
Interactions
Interactions with Supplements, Foods, & Other Compounds
Interactions with Medicines
Certain medicines interact with this supplement.
Replenish Depleted Nutrients
none
Reduce Side Effects
none
Support Medicine
none
Reduces Effectiveness
- Cardec DM
Tannins are a group of unrelated chemicals that give plants an astringent taste. Herbs containing high amounts of tannins may interfere with the absorption of ephedrine or pseudoephedrine taken by mouth. Herbs containing high levels of tannins include , black tea, uva ursi(Arctostaphylos uva-ursi), black walnut (Juglans nigra),red raspberry(Rubus idaeus), oak(Quercus spp.), and witch hazel(Hamamelis virginiana).
- NadololIn a study of healthy volunteers, ingestion of green tea along with nadolol decreased the absorption of the drug and decreased its blood pressure-lowering effect. Based on this report, people taking nadolol should not consume green tea.
- Warfarin
One man taking warfarin and one-half to one gallon of green tea (Camellia sinensis) per day developed signs based on laboratory testing suggesting his blood was too thick because the green tea was blocking the effect of warfarin. Removal of the green tea caused normalization of his blood tests. Those taking green tea and warfarin together should have their blood monitored regularly to avert any problems and should consult with a doctor, healthcare practitioner and/or pharmacist before taking any medication.
Potential Negative Interaction
none
Explanation Required
none
Side Effects
Side Effects
Green tea is generally free of side effects. The most common adverse effects reported from consuming large amounts (several cups per day) of green tea are insomnia, anxiety, and other symptoms caused by the caffeine content in the herb.
An extract of green tea taken by healthy women with a meal inhibited the absorption of non-heme iron (e.g., the form of iron in plant foods) by 26%.34 Frequent use of green tea could, in theory, promote the development of iron deficiency in susceptible individuals.
There have been at least 34 case reports of people developing liver damage (sometimes severe) while consuming weight-loss products that contained concentrated extracts of green tea.35 A cause–effect relationship was not proven, and most of the products contained other ingredients in addition to green tea extract. However, researchers have concluded that green tea extract was the probable cause of liver damage in some of the cases.36 Scientists have cautioned against the use of large amounts, or concentrated extracts, of green tea.
Importantly, liver damage due to green tea extract and EGCG supplementation has been reported. A review of these reports indicates high doses (500–3,000 mg green tea extract or 250–1,800 mg of EGCG taken all at once daily) used for two weeks or longer and most often on an empty stomach are more likely to cause liver injury. While individual, possibly genetic, factors may increase susceptibility, it is suggested those with pre-existing liver disease and obesity may be at greatest risk.37
In addition, there is a case report in which a person developed thrombotic thrombocytopenic purpura (a condition in which a bruising develops as a result of a low platelet count) after consuming a weight-loss product that contained green tea extract for 2 months. Green tea was not proven to be the cause of this problem.38
References
1. Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med 1992;21:334-50.
2. Kono S, Shinchi K, Ikeda N, et al. Green tea consumption and serum lipid profiles: A cross-sectional study in Northern Kyushu, Japan. Prev Med 1992;21:526-31.
3. Yamaguchi Y, Hayashi M, Yamazoe H, et al. Preventive effects of green tea extract on lipid abnormalities in serum, liver and aorta of mice fed an atherogenic diet. Nip Yak Zas 1991;97:329-37.
4. Sagesaka-Mitane Y, Milwa M, Okada S. Platelet aggregation inhibitors in hot water extract of green tea. Chem Pharm Bull 1990;38:790-3.
5. Stensvold I, Tverdal A, Solvoll K, et al. Tea consumption. Relationship to cholesterol, blood pressure, and coronary and total mortality. Prev Med 1992;21:546-53.
6. Tsubono Y, Tsugane S. Green tea intake in relation to serum lipid levels in middle-aged Japanese men and women. Ann Epidemiol 1997;7:280-4.
7. Serafini M, Ghiselli A, Ferro-Luzzi A. In vivo antioxidant effect of green tea in man. Eur J Clin Nutr 1996;50:28-32.
8. Benzie IF, Szeto YT, Strain JJ, Tomlinson B. Consumption of green tea causes rapid increase in plasma antioxidant power in humans. Nutr Cancer 1999;34:83-7.
9. Sasazuki S, Komdama H, Yoshimasu K, et al. Relation between green tea consumption and severity of coronary atherosclerosis among Japanese men and women. Ann Epidemiol 2000;10:401-8.
10. Suganuma M, Okabe S, Sueoka N, et al. Green tea and cancer chemoprevention. Mutat Res 1999;428:339-44.
11. Weisberger JH, Rivenson A, Garr K, et al. Tea, or tea and milk, inhibit mammary gland and colon carcinogenesis in rats. Cancer Lett 1997;114:323-7.
12. Yang CS, Lee MJ, Chen L, Yang GY. Polyphenols as inhibitors of carcinogenesis. Environ Health Perspect 1997;105(Suppl 4):971-6 [review].
13. Menon LG, Kuttan R, Kuttan G. Anti-metastatic activity of curcumin and catechin. Cancer Lett 1999;141:159-65.
14. Mukhtar H, Ahmad N. Green tea in chemoprevention of cancer. Toxicol Sci 1999;52(2 Suppl):111-7.
15. Katiyar SK, Mukhtar H. Tea consumption and cancer. World Rev Nutr Diet 1996;79:154-84 [review].
16. Kohlmeier L, Weterings KG, Steck S, Kok FJ. Tea and cancer prevention: an evaluation of the epidemiologic literature. Nutr Cancer 1997;27:1-13 [review].
17. Tsubono Y, Nishino Y, Komatsu S, et al. Green tea and the risk of gastric cancer in Japan. New Engl J Med 2001;344:632-6.
18. Galanis DJ, Kolonel LN, Lee J, Nomura A. Intakes of selected foods and beverages and the incidence of gastric cancer among the Japanese residents of Hawaii: a prospective study. Int J Epidemiol 1998;27:173-80.
19. Li N, Sun Z, Han C, Chen J. The chemopreventive effects of tea on human oral precancerous mucosa lesions. Proc Soc Exp Biol Med 1999;220:218-24.
20. Otake S, Makimura M, Kuroki T, et al. Anticaries effects of polyphenolic compounds from Japanese green tea. Caries Res 1991;25:438-43.
21. Ooshima T, Minami T, Aono W, et al. Reduction of dental plaque deposition in humans by oolong tea extract. Caries Res 1994;28:146-9.
22. Stoner GD, Mukhtar H. Polyphenols as cancer chemopreventive agents. J Cell Bioch 1995;22:169-80.
23. You SQ. Study on feasibility of Chinese green tea polyphenols (CTP) for preventing dental caries. Chin J Stom 1993;28(4):197-9.
24. Hamilton-Miller JM. Antimicrobial properties of tea (Camellia sinensis L.). Antimicrob Agents Chemother 1995;39:2375-7.
25. Imai K, Nakachi K. Cross sectional study of effects of drinking green tea on cardiovascular and liver diseases. BMJ 1995;310:693-6.
26. Goto K, Kanaya S, Nishikawa T, et al. The influence of tea catechins on fecal flora of elderly residents in long-term care facilities. Ann Long-Term Care 1998;6:43-8.
27. Goto K, Kanaya S, Ishigami T, Hara Y. The effects of tea catechins on fecal conditions of elderly residents in a long-term care facility. J Nutr Sci Vitaminol 1999;45:135-41.
28. Kaltwasser JP, Werner E, Schalk K, et al. Clinical trial on the effect of regular tea drinking on iron accumulation in genetic haemochromatosis. Gut 1998;43:699-704.
29. Bettuzzi S, Brausi M, Rizzi F, et al. 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 Res2006;66:1234-40.
30. Shanafelt TD, Lee YK, Call TG, et al. Clinical effects of oral green tea extracts in four patients with low grade B-cell malignancies. Leuk Res 2006;30:707-12.
31. Murray MT. The Healing Power of Herbs. Rocklin, CA: Prima Publishing, 1995, 192-6.
32. Imai K, Suga K, Nakachi K. Cancer-preventive effects of drinking green tea among a Japanese population. Prev Med 1997;26:769-75.
33. Imai K, Nakachi K. Cross sectional study of effects of drinking green tea on cardiovascular and liver diseases. BMJ 1995;310:693-6.
34. Samman S, Sandstrom B, Toft MB, et al. Green tea or rosemary extract added to foods reduces nonheme-iron absorption. Am J Clin Nutr 2001;73:607-12.
35. Bonkovsky HL. Hepatotoxicity associated with supplements containing Chinese green tea (Camellia sinensis). Ann Intern Med 2006;144:68-71.
36. Schonthal AH. Adverse effects of concentrated green tea extracts. Mol Nutr Food Res 2011;55:874-885.
37. Oketch-Rabah HA, Roe AL, Rider CV, et al. United States Pharmacopeia (USP) comprehensive review of the hepatotoxicity of green tea extracts. Toxicol Rep 2020;7:386–402.
38. Liatsos GD, Moulakakis A, Ketikoglou I, Klonari S. Possible green tea-induced thrombotic thrombocytopenic purpura. Am J Health Syst Pharm 2010;67:531-4.
Last Review: 05-23-2015
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The information presented by TraceGains is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2024.
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