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Green Tea
(Camellia sinensis)
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| Introduction |
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| Green tea has long been used in much of the world as a popular beverage and a respected medicinal agent.(1) Early Chinese medical literature lists green tea as an agent to promote digestion, improve mental faculties, decrease flatulence and regulate body temperature. The earliest known record of use dates back to around 2700 B.C. Today, ceremonies, celebrations, relaxation time and ordinary meals usually consist of tea in most parts of the world, except where coffee has become the more popular beverage, like the United States. |
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| Reported Uses |
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Green tea has antioxidant properties. This means it has the ability to protect against oxidative damage to tissues and red blood cells.(2, 3, 4) Though debated, it is important to note that some studies suggest that adding milk to green tea significantly decreases its antioxidant potential.(5)
Green tea may also support cardiovascular health and may help reduce cholesterol levels,(6, 7) potentially assisting people in lowering their risk of atherosclerosis and other cardiovascular diseases. It may also help the body maintain healthy blood flow through the cardiovascular system.(8, 9)
A number of studies have looked at green tea's potential for reducing the risk of certain kinds of cancer.(10, 11, 12, 13, 14, 15) It may lessen the chance that carcinogenic chemicals and other substances will cause the formation of tumors.(16, 17) One particular study showed promising results in inhibiting the growth of breast cancer cells in pre- and post-menopausal women.(18, 19) Additionally, green tea may enhance the effects of chemotherapy while reducing the tissue damage that can result from chemotherapy.(20, 21, 22)
Other benefits that have been researched include the potential for boosting immunity and preventing dental cavities.(23, 24, 25) Also, the caffeine and catechin polyphenols contained in green tea may work together to enhance the body's thermogenic activity, thus increasing the rate at which the body breaks down fat.(26) Green tea may have stimulant and antifungal properties. It can act as a diuretic, increasing urine flow and the body's ability to get rid of water. Green tea also has astringent properties, assisting in the contraction of certain tissues to slow secretions or blood flow.(27)
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| Dosage Info |
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| Dosage Range |
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Most Common Dosage |
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Dosage Forms |
| 250-500mg (standardized extract) daily.
Tea: 1 to 3 cups daily using one teaspoon of leaf per cup.(28) |
500mg (standardized extract) daily.
Tea: 1 to 3 cups daily using one teaspoon of leaf per cup. |
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| Toxicities & Precautions |
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| Be sure to tell your pharmacist, doctor, or other health care providers about any dietary supplements you are taking. There may be a potential for interactions or side effects. |
General
This dietary supplement is considered safe when used in accordance with proper dosing guidelines.(29)
If the tea product you are taking contains caffeine, use with coffee or other caffeinated beverages is not recommended.
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Health Conditions
If you have a peptic ulcer or have cardiovascular disease and the dietary supplement contains caffeine, talk to your doctor before taking this dietary supplement. If you have a bleeding disorder talk to your doctor before taking this dietary supplement.
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Side Effects
Side effects are possible with any dietary supplement. If you are using a product that contains caffeine, this dietary supplement may cause insomnia, decreased appetite, increased heart rate, increased blood pressure(30) or nervousness in sensitive individuals. Tell your doctor if these side effects become severe or do not go away.
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Pregnancy/Breast-Feeding
To date, the medical literature has not reported any adverse effects related to fetal development during pregnancy or to infants who are breast-fed. Yet little is known about the use of this dietary supplement while pregnant or breast-feeding. Therefore, it is recommended that you inform your healthcare practitioner of any dietary supplements you are using while pregnant or breast-feeding. |
Age Limitations
To date, the medical literature has not reported any adverse effects specifically related to the use of this dietary supplement in children. Since young children may have undiagnosed allergies or medical conditions, this dietary supplement should not be used in children under 10 years of age unless recommended by a physician. |
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| Footnotes |
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1 Cooper R, et al. Medicinal Benefits of Green Tea: Part 1. Review of Noncancer Health Benefits. J Alt Comp Med. 2005;11(3):521-8.
2 Cheng TO. Antioxidants in Chinese Green Tea. J Am Coll Cardiol. Apr1998;31(5):1214.
3 Grinberg LN, et al. Protective Effects of Tea Polyphenols against Oxidative Damage to Red Blood Cells. Biochem Pharmacol. Nov1997;54(9):973-78.
View Abstract
4 Hakim IA, Harris RB, Brown S, et al. Effect of Increased Tea Consumption on Oxidative DNA Damage among Smokers: A Randomized Controlled Study. J Nutr. Oct2003;133(10):3303S-9S.
View Abstract
5 Hertog MG, et al. Antioxidant Flavonols and Ischemic Heart Disease in a Welsh Population of Men: The Caerphilly Study. Am J Clin Nutr. May1997;65(5):1489-94.
View Abstract
6 Hertog MG, et al. Dietary Antioxidant Flavonoids and Risk of Coronary Heart Disease: The Zutphen Elderly Study. Lancet. Oct1993;342(8878):1007-1011.
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7 Maron DJ, Lu GP, Cai NS, et al. Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial. Arch Intern Med. Jun2003;163(12):1448-53.
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8 Ali M, et al. A Potent Inhibitor of Thrombin Stimulated Platelet Thromboxane Formation from Unprocessed Tea. Prostaglandins Leukot Med. Apr1987;27(1):9-13.
View Abstract
9 Sagesaka-Mitane Y, et al. Platelet Aggregation Inhibitors in Hot Water Extract of Green Tea. Chem Pharm Bull. (Tokyo). Mar1990;38(3):790-93.
View Abstract
10 Hu G, et al. Inhibition of Oncogene Expression by Green Tea and (-)-Epigallocatechin Gallate in Mice. Nutr Cancer. 1995;24(2):203-09.
View Abstract
11 Wu AH, Yu MC, Tseng CC, Hankin J, Pike MC. Green tea and risk of breast cancer in Asian Americans. Int J Cancer. Sep2003;106(4):574-9.
View Abstract
12 Gao CM, Takezaki T, Wu JZ, Li ZY, Liu YT, Li SP, Ding JH, Su P, Hu X, Xu TL, Sugimura H, Tajima K. Glutathione-S-transferases M1 (GSTM1) and GSTT1 genotype, smoking, consumption of alcohol and tea and risk of esophageal and stomach cancers: a case-control study of a high-incidence area in Jiangsu Province, China. Cancer Lett. Dec2002;188(1-2):95-102.
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13 Adhami VM, Ahmad N, Mukhtar H. Molecular targets for green tea in prostate cancer prevention. J Nutr. 2003;133(7):2417S-24S.
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14 Kemberling JK, Hampton JA, Keck RW, Gomez MA, Selman SH. Inhibition of Bladder Tumor Growth by the Green Tea Derivative Epigallocatechin-3-Gallate. J Urol. Sep2003;170(3):773-776.
View Abstract
15 Jian L. Protective effect of green tea against prostate cancer: a case-control study in southeast China. Int J Cancer. 2004 Jan 1;108(1):130-5.
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16 Komori A, et al. Anticarcinogenic Activity of Green Tea Polyphenols. Jpn J Clin Oncol. Jun1993;23(3):186-90.
View Abstract
17 Agarwal R, et al. Cancer Chemoprevention by Polyphenols in Green Tea and Artichoke. Adv Exp Med Biol. 1996;401:35-50.
18 Nakachi K , et al. Influence of Drinking Green Tea on Breast Cancer Malignancy among Japanese Patients. Jpn J Cancer Res. Mar1998;89(3):254-61.
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19 Nagata C, et al. Association of Coffee, Green Tea, and Caffeine Intakes with Serum Concentrations of Etradiol and Sex Hormone-binding Globulin in Premenopausal Japanese Women. Nutr Cancer. 1998;30(1):21-24.
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20 Stammler G, et al. Green Tea Catechins (EGCG and EGC) Have Modulating Effects on the Activity of Doxorubicin in Drug-resistant Cell Lines. Anticancer Drugs. Mar1997;8(3):265-68.
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21 Sadzuka Y, et al. The Effects of Theanine, as a Novel Biochemical Modulator, on the Antitumor Activity of Adriamycin. Cancer Lett. Aug1996;105(2):203-09.
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22 Mitscher LA, et al. Chemoprotection: A Review of the Potential Therapeutic Antioxidant Properties of Green Tea (Camellia sinensis) and Certain of Its Constituents. Med Res Rev. Jul1997;17(4):327-65.
23 Tagashira M, et al. Inhibition by Hop Bract Polyphenols of Cellular Adherence and Water-insoluble Glucan Synthesis of Mutans Streptococci. Biosci Biotechnol Biochem. Feb1997;61(2):332-35.
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24 Yu H, et al. Anticariogenic Effects of Green Tea. Fukuoka Igaku Zasshi. Apr1992;83(4):174-80.
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25 Stoner GD, et al. Polyphenols as Cancer Chemopreventive Agents. J Cell Biochem Supp. 1995;22:169-80.
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26 Dulloo AG, Sevdoux J, Girardier L, et al. Green Tea and Thermogenesis: Interactions Between Catechin-polyphenols, Caffeine and Sympathetic Activity. Int J Obes Relat Metab Disord. Feb2000;24(2):252-8.
View Abstract
27 Green tea. Altern Med Rev. Aug2000;5(4):372-5.
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28 PDR for Herbal Medicines, 2nd edition. Montvale, NJ:
Medical Economics Company; 2000:371.
29 Green tea. Altern Med Rev. Aug2000;5(4):372-5.
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30 Hodgson JM, Puddey IB, Burke V, et al. Effects on Blood Pressure of Drinking Green and Black Tea. J Hypertens. Apr1999;17(4):457-63.
View Abstract
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