Green tea has been consumed for more than three thousand years for both its refreshing and health promoting benefits. In fact, a historical perspective1 on green and black tea reported that they are among the most widely consumed beverages in the world, second only to water. Dogma has it that, for 4,000 years people knew tea might have health-promoting properties since it was frequently used as fluid supply for patients suffering from infectious diseases. This article will review a number of green tea's many benefits to human health, including its antioxidant and anti-inflammatory properties, its anti-cancer activity, and its ability to promote both cardiovascular health and weight loss. Before jumping into its benefits, however, let's first take a look at the difference between green, black and oolong tea.
Green, black and oolong tea
Green, black and oolong tea all come from the same species, Camellia sinensis. Green tea, however, is different than black and oolong teas because it is not fermented. Black tea is fully fermented and oolong tea is partially fermented, whereas green tea is produced by steaming fresh leaves. The steaming doesn't decrease polyphenols in green tea, such as flavanols, flavandiols, flavonoids, and phenolic acids, which are abundant. One group of flavanols are known as catechins. These include epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC), which are responsible for many of green tea's benefits. Growing conditions, leaf age, and storage during and after transport affect the amount of polyphenols and catechins in green tea. For example, green tea catechins can range from 69 to 103 mg/gram of tea,2,3 although green tea extracts may provide significantly higher amounts.
Green tea has significant antioxidant properties.4 Laboratory research5 found that green tea slowed down the oxidation of LDL cholesterol ('bad cholesterol'), which is associated with atherosclerosis, or the build-up of plaque on arterial walls. A cup of green tea contains 50 to 100 mg of polyphenols (approximately 6,300 to 12,600 times higher than the dose used in the laboratory study). Therefore, one cup of green tea a day may provide a therapeutic dose of antioxidant polyphenols, and green tea extracts with higher polyphenol content likely provide even greater antioxidant activity. In fact, in human research,6 the consumption of green tea extract (high in polyphenols) led to a greater increase in plasma antioxidant activity than when given as a standard tea. This makes sense when considering that the antioxidant score (aka, ORAC score) for a cup of brewed green tea is 1253 ORAC units,7 while one gram of green tea extract has 3,996 ORAC units.8 Depending upon the actual extract, some green tea products may even have a higher ORAC value.
Catechins in green tea have anti-inflammatory activity. This includes a reduction in the following inflammatory markers: leukotriene-B4, 5-lipoxygenase,9 COX-2 and nitric oxide synthase.10 In addition, EGCG and other catechins in green tea might reduce inflammation and protect cartilage by inhibiting proteoglycan and collagen breakdown,11 which may have positive implications for joints as seen in laboratory models of rheumatoid arthritis.12 Other examples of green tea's anti-inflammatory effect include a reduction gum (gingival) inflammation,13 protection against sunburn inflammation,14 and a reduction in a marker of chronic inflammation as a cardiovascular risk factor.15
Research suggests that green tea may protect against some kinds of cancer. Tea polyphenols have antimutagenic effects and protect DNA,16 reduce oxidative DNA damage, lipid peroxidation, and free radical generation.17 In animal or laboratory research green tea catechins prevented new blood vessel growth (angiogenesis) in tumors and inhibited tumor cell proliferation resulting cell death (apoptosis).18,19,20,21,22,23 In human research, green tea was shown to reduce mutagenic activity in smokers.24
A population based study25 of 40,530 healthy adults aged 40 to 79 years found that the consumption of three or more cups of green tea daily for 11 years significantly decreases the risk of cardiovascular and all-cause mortality compared to drinking less than one cup daily, and this association was primarily related to a decrease in risk for stroke (cerebral infarction). In another population study of 1371 men, aged 40 years or older, increased daily consumption of green tea resulted in significantly decreased serum levels of total cholesterol, LDL cholesterol (‘bad cholesterol'), and triglycerides, while increasing HDL cholesterol (‘good cholesterol'). Moreover, there was a decrease in other serum markers of liver disease, especially when more than 10 cups of green tea daily was consumed.
Weight loss properties
A population study26 of 1,210 adults examined the relationship between habitual tea consumption (mostly green and oolong tea) and changes in total body fat and fat distribution in humans. Results were that habitual tea drinkers for more than 10 years showed a 19.6 percent reduction in body fat percentage and a 2.1 percent reduction in waist-to-hip ratio compared with nonhabitual tea drinkers. Other research27 has shown that higher intakes of polyphenols (favonols/flavones, catechins) from tea and other sources were associated with a significantly lower increase in BMI (body mass index), a measure of healthy body weight. Furthermore, other research has shown that green tea extract stimulates thermogenesis (i.e. fat burning)28 and helped obese individuals lose weight.29
Green tea has many health benefits to offer, and it is a worthwhile endeavor to include it as part of your daily routine. Drinking a few cups of green tea each day or, better yet, using a green tea extract high in polyphenols will provide you with antioxidant protection while providing a plethora of other benefits.
- Weisburger JH. Tea and health: a historical perspective. Cancer Lett 1997;114(1–2):315–7.
- Khokhar S, Magnusdottir SG. Total phenol, catechin, and caffeine contents of teas commonly consumed in the United kingdom. J Agric Food Chem 2002;50:565–70.
- Henning M, Fajardo-Lira C, Lee HW, et al. Catechin content of 18 teas and a green tea extract supplement correlates with the antioxidant capacity. Nutr Cancer 2003;45:226–35.
- Vertuani S, Bosco E, Braccioli E, Manfredini S. Water soluble antioxidant capacity of different teas—determination by photochemiluminescence. Nutrafoods. 2004;3(2):5–11.
- Luo M, Wahlqvist M, and O’Brien R. Inhibition of LDL oxidation by green tea extract. Lancet. 1997 Feb 1;349(9048):360–1.
- Henning SM, Niu Y, Lee NH, et al. Bioavailability and antioxidant activity of tea flavanols after consumption of green tea, black tea, or a green tea extract supplement. Am J Clin Nutr 2004;80(6):1558–64.
- U.S. Department of Agriculture, Agricultural Research Service. 2010. Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2: pg. 36.
- Brunswick Laboratories. Database for ORAC 5.0 and Cellular Antioxidant Assay (CAA): Green Tea Extract. Retrieved February 12, 2016 from http://www.brunswicklabs.com/tech-library/oracdatabase/green-tea-extract.
- Choi JH, Chai YM, Joo GJ, et al. Effects of green tea catechin on polymorphonuclear leukocyte 5’-lipoxygenase activity, leukotriene B4 synthesis, and renal damage in diabetic rats. Ann Nutr Metab 2004;48:151–5.
- Ahmed S, Rahman A, Hasnain A, et al. Green tea polyphenol epigallocatechin-3-gallate inhibits the IL-1 beta-induced activity and expression of cyclooxygenase-2 and nitric oxide synthase-2 in human chondrocytes. Free Radic Biol Med 2002;33:1097–105.
- Adcocks C, Collin P, Buttle DJ. Catechins from green tea (Camellia sinensis) inhibit bovine and human cartilage proteoglycan and type II collagen degradation in vitro. J Nutr 2002;132:341–6.
- Haqqi TM, Anthony DD, Gupta S, et al. Prevention of collageninduced arthritis in mice by a polyphenolic fraction from green tea. Proc Natl Acad Sci U S A 1999;96:4524–9.
- Krahwinkel T, Willershausen B. The effect of sugar-free green tea chew candies on the degree of inflammation of the gingiva. Eur J Med Res 2000;5:463–7.
- Rhodes LE, Darby G, Massey KA, Clarke KA, Dew TP, Farrar MD, Bennett S, Watson RE, Williamson G, Nicolaou A. Oral green tea catechin metabolites are incorporated into human skin and protect against UV radiation-induced cutaneous inflammation in association with reduced production of pro-inflammatory eicosanoid 12-hydroxyeicosatetraenoic acid. Br J Nutr. 2013 Sep 14;110(5):891–900.
- Nantz MP, Rowe CA, Bukowski JF, Percival SS. Standardized capsule of Camellia sinensis lowers cardiovascular risk factors in a randomized, double-blind, placebo-controlled study. Nutrition. 2009 Feb;25(2):147–54.
- Gupta S, Saha B, Giri AK. Comparative antimutagenic and anticlastogenic effects of green tea and black tea: a review. Mutat Res 2002;512:37–65.
- Klauni g JE, Xu Y, Han C, et al. The effect of tea consumption on oxidative stress in smokers and nonsmokers. Proc Soc Exp Biol Med 1999;220:249–54.
- Garbisa S, Biggin S, Cavallarin N, et al. Tumor invasion: molecular shears blunted by green tea. Nat Med 1999;5:1216.
- Cao Y, Cao R. Angiogenesis inhibited by drinking tea. Nature 1999;398:381.
- L’Allemain G. [Multiple actions of EGCG, the main component of green tea]. Bull Cancer 1999;86:721–4.
- Pisters KM, Newman RA, Coldman B, et al. Phase I trial of oral green tea extract in adult patients with solid tumors. J Clin Oncol 2001;19:1830–8.
- Kemberling JK, Hampton JA, Keck RW, et al. Inhibition of bladder tumor growth by the green tea derivative epigallocatechin-3-gallate. J Urol 2003;170:773–6.
- Chung LY, Cheung TC, Kong SK, et al. Induction of apoptosis by green tea catechins in human prostate cancer DU145 cells. Life Sci 2001;68:1207–14.
- Lee IP, Kim YH, Kang MH, et al. Chemopreventive effect of green tea (Camellia sinensis) against cigarette smoke induced mutations in humans. J Cell Biochem Suppl 1997;27:68–75.
- Kuriyama S, Shimazu T, Ohmori K, et al. Green tea consumption and mortality due to cardiovascular disease, cancer, and all-cause mortality. JAMA 2006;296:1255–65.
- Wu CH, Lu FH, Chang CS, Chang TC, Wang RH, Chang CJ. Relationship among habitual tea consumption, percent body fat, and body fat distribution. Obes Res. 2003 Sep;11(9):1088–95.
- Hughes LA, Arts IC, Ambergen T, Brants HA, Dagnelie PC, Goldbohm RA, van den Brandt PA, Weijenberg MP; Netherlands Cohort Study. Higher dietary flavone, flavonol, and catechin intakes are associated with less of an increase in BMI over time in women: a longitudinal analysis from the Netherlands Cohort Study. Am J Clin Nutr. 2008 Nov;88(5):1341–52.
- Dulloo AG, Duret C; Rohrer D, et al. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24 h energy expenditure and fat oxidation in humans. Am J Clin Nutr 1999; 70(6):1040–5.
- Auvichayapat P, Prapochanung M, Tunkamnerdthai O, et al. Effectiveness of green tea on weight reduction in obese Thais: A randomized, controlled trial. Physiol Behav 2008;93(3):486–91.