All whole plant foods contain fiber, many different fruits and vegetables are rich in vitamin C, and many orange vegetables and fruits are rich in beta-carotene. Some nutrients and phytochemicals are more specific. Lycopene is far more concentrated in cooked tomatoes than any other food, isothiocyanates are formed only by members of the cruciferous vegetable family, punicalagin is found only in pomegranate, and epigallocatechin-3-gallate (EGCG) is found almost exclusively in tea, especially green tea.1
What’s the difference between green, black, and white teas?
All types of tea are made from the Camellia sinensis plant, and the different types are based mostly on processing methods. During the “fermentation” process, the tea leaves are broken or rolled, and oxidation changes the phytochemical makeup of the tea. White tea is made from buds and young leaves, and green tea from more mature leaves; both white and green teas are unfermented. During fermentation, the flavonoids characteristic of green tea (catechins such as EGCG) are converted to those that are characteristic of black tea (theaflavins and thearubigins). The longer the tea leaves are fermented, the less EGCG there will be. Oolong tea is semifermented, and black tea is fully fermented.2
|EGCG (mg/100 g brewed tea)1|
|Decaffeinated green tea||26.05|
Drinking green tea regularly has been linked to reduced risk of heart disease, stroke, lung cancer, breast cancer, prostate cancer, diabetes, and all-cause mortality.3-11 Green tea is also thought to help prevent or slow brain aging.12,13
Green tea catechins are thought to affect energy metabolism, and green tea supplementation has been investigated for potential effects on weight loss, but no significant reductions in weight have been reported.14
An analysis of 5 studies found a dose-dependent 10 percent decrease in coronary artery disease risk for each cup of green tea consumed daily; there was no such effect for black tea.3 Randomized controlled trials have shed light on how this might work, showing that drinking green tea or using green tea extract supplements:
Many anti-cancer effects have been attributed to green tea catechins:
Brewed tea or supplements?
Green tea polyphenols can add to the spectrum of phytochemicals provided by green vegetables and other plant foods; a daily cup or two of green tea is a healthful adjunct to a high-nutrient diet. Green tea extract supplements are also an option, but they are very concentrated, commonly providing EGCG levels equivalent to five, ten, or even twenty cups of tea. The more concentrated supplements may be appropriate in some cases, but more than necessary for most people. Green tea extract supplements are sometimes but not always decaffeinated.
Regular or decaf?
Caffeine content varies with the type of green tea, brewing method, and steeping time, but in general green tea contains less caffeine than black tea, and black tea contains less than coffee. A study of commercially available tea bags found that black teas had a caffeine content ranging from 27 to 61 mg per 6 ounce cup, and green tea 36 to 41 mg, when steeped for 5 minutes.36 Catechins are released somewhat slowly, so a longer steep time is better; green tea steeped for five minutes has more than four times the catechins compared to one minute.37 If you prefer iced tea, antioxidant activity was found to be similar in green teas steeped in hot water for seven minutes compared to cold water for two hours.38
Note in the table above that the EGCG content is lower in decaffeinated green teas, but still substantially more than black tea. To add some green tea catechins to your diet while minimizing the caffeine content, you can opt for a decaffeinated green tea. Some teas use the solvent methylene chloride, which has been found to be carcinogenic in animals.39 Ethyl acetate is another common solvent used in teas; these teas are often labeled “naturally decaffeinated,” because ethyl acetate is a naturally occurring plant compound; it is only thought to pose a risk in very high doses (via inhalation) in occupational settings.40 Teas using the carbon dioxide decaffeination process are probably the best choice. Tea company websites often specify their decaffeination method.
Drink green tea plain
It is best to drink green tea plain, since there is evidence that adding milk (dairy or not) may blunt some of the benefit, possibly because of an interaction between proteins and tea polyphenols. The study suggested that adding milk blocked the improvements in endothelial function commonly observed with tea intake.41 It is thought that soy milk has a similar effect.42
Loose tea or tea bags?
Brewing loose tea or using powdered green tea (matcha) produces less waste than tea bags, and some of the newer “sachet” tea bags contain plastic compounds that may have endocrine disrupting effects. Also, some paper tea bags are coated with epichlorohydrin, a potential carcinogen.43-46 If you use paper tea bags, it is best to look for teas that use unbleached paper tea bags that do not contain epichlorohydrin.
Remember, it is not one particular food or nutrient that will best assure your long-term health and protection against cancer, but the regular consumption of a wide variety of beneficial plant compounds. Green tea clearly has beneficial properties, but these benefits may be more pronounced in those who have a poor diet compared to those already consuming an array of phytochemicals in a Nutritarian diet.
USDA Database for the Flavonoid Content of Selected Foods, Release 3.1 2014 [http://www.ars.usda.gov/SP2UserFiles/Place/80400525/Data/Flav/Flav_R03-1.pdf]
Higdon J, Drake VJ: Tea. In An Evidence-Based Approach to Dietary Phytochemicals and Other Dietary Factors. Thieme; 2012: 42-51
Wang ZM, Zhou B, Wang YS, et al. Black and green tea consumption and the risk of coronary artery disease: a meta-analysis. Am J Clin Nutr 2011, 93:506-515.
Arab L, Liu W, Elashoff D. Green and black tea consumption and risk of stroke: a meta-analysis. Stroke 2009, 40:1786-1792.
Tang N, Wu Y, Zhou B, et al. Green tea, black tea consumption and risk of lung cancer: a meta-analysis. Lung Cancer 2009, 65:274-283.
Sun CL, Yuan JM, Koh WP, Yu MC. Green tea, black tea and breast cancer risk: a meta-analysis of epidemiological studies. Carcinogenesis 2006, 27:1310-1315.
Ogunleye AA, Xue F, Michels KB. Green tea consumption and breast cancer risk or recurrence: a meta-analysis. Breast Cancer Res Treat 2010, 119:477-484.
Khan N, Adhami VM, Mukhtar H. Review: green tea polyphenols in chemoprevention of prostate cancer: preclinical and clinical studies. Nutr Cancer 2009, 61:836-841.
Zheng J, Yang B, Huang T, et al. Green Tea and Black Tea Consumption and Prostate Cancer Risk: An Exploratory Meta-Analysis of Observational Studies. Nutr Cancer 2011:1-10.
Kuriyama S, Shimazu T, Ohmori K, et al. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA 2006, 296:1255-1265.
Iso H, Date C, Wakai K, et al. The relationship between green tea and total caffeine intake and risk for self-reported type 2 diabetes among Japanese adults. Ann Intern Med 2006, 144:554-562.
Assuncao M, Andrade JP. Protective action of green tea catechins in neuronal mitochondria during aging. Front Biosci (Landmark Ed) 2015, 20:247-262.
Mandel SA, Amit T, Weinreb O, Youdim MB. Understanding the broad-spectrum neuroprotective action profile of green tea polyphenols in aging and neurodegenerative diseases. J Alzheimers Dis 2011, 25:187-208.
Jurgens TM, Whelan AM, Killian L, et al. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database Syst Rev 2012, 12:CD008650.
Liu K, Zhou R, Wang B, et al. Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials. Am J Clin Nutr 2013, 98:340-348.
Zheng XX, Xu YL, Li SH, et al. Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials. Am J Clin Nutr 2011.
Khalesi S, Sun J, Buys N, et al. Green tea catechins and blood pressure: a systematic review and meta-analysis of randomised controlled trials. Eur J Nutr 2014, 53:1299-1311.
Alexopoulos N, Vlachopoulos C, Aznaouridis K, et al. The acute effect of green tea consumption on endothelial function in healthy individuals. Eur J Cardiovasc Prev Rehabil 2008, 15:300-305.
Tinahones FJ, Rubio MA, Garrido-Sanchez L, et al. Green tea reduces LDL oxidability and improves vascular function. J Am Coll Nutr 2008, 27:209-213.
Gomikawa S, Ishikawa Y, Hayase W, et al. Effect of ground green tea drinking for 2 weeks on the susceptibility of plasma and LDL to the oxidation ex vivo in healthy volunteers. Kobe J Med Sci 2008, 54:E62-72.
Singh T, Katiyar SK. Green tea catechins reduce invasive potential of human melanoma cells by targeting COX-2, PGE2 receptors and epithelial-to-mesenchymal transition. PLoS One 2011, 6:e25224.
Khan N, Mukhtar H. Cancer and metastasis: prevention and treatment by green tea. Cancer Metastasis Rev 2010, 29:435-445.
Chen L, Zhang HY. Cancer preventive mechanisms of the green tea polyphenol (-)-epigallocatechin-3-gallate. Molecules 2007, 12:946-957.
Singh BN, Shankar S, Srivastava RK. Green tea catechin, epigallocatechin-3-gallate (EGCG): mechanisms, perspectives and clinical applications. Biochem Pharmacol 2011, 82:1807-1821.
Ho CK, Choi SW, Siu PM, Benzie IF. Effects of single dose and regular intake of green tea (Camellia sinensis) on DNA damage, DNA repair, and heme oxygenase-1 expression in a randomized controlled human supplementation study. Mol Nutr Food Res 2014, 58:1379-1383.
Jung YD, Ellis LM. Inhibition of tumour invasion and angiogenesis by epigallocatechin gallate (EGCG), a major component of green tea. Int J Exp Pathol 2001, 82:309-316.
Rodriguez SK, Guo W, Liu L, et al. Green tea catechin, epigallocatechin-3-gallate, inhibits vascular endothelial growth factor angiogenic signaling by disrupting the formation of a receptor complex. International journal of cancer Journal international du cancer 2006, 118:1635-1644.
Domingo DS, Camouse MM, Hsia AH, et al. Anti-angiogenic effects of epigallocatechin-3-gallate in human skin. International journal of clinical and experimental pathology 2010, 3:705-709.
Murugan RS, Vinothini G, Hara Y, Nagini S. Black tea polyphenols target matrix metalloproteinases, RECK, proangiogenic molecules and histone deacetylase in a rat hepatocarcinogenesis model. Anticancer Res 2009, 29:2301-2305.
Hussain T, Gupta S, Adhami VM, Mukhtar H. Green tea constituent epigallocatechin-3-gallate selectively inhibits COX-2 without affecting COX-1 expression in human prostate carcinoma cells. Int J Cancer 2005, 113:660-669.
Peng G, Dixon DA, Muga SJ, et al. Green tea polyphenol (-)-epigallocatechin-3-gallate inhibits cyclooxygenase-2 expression in colon carcinogenesis. Mol Carcinog 2006, 45:309-319.
Heinrich U, Moore CE, De Spirt S, et al. Green tea polyphenols provide photoprotection, increase microcirculation, and modulate skin properties of women. J Nutr 2011, 141:1202-1208.
Morley N, Clifford T, Salter L, et al. The green tea polyphenol (-)-epigallocatechin gallate and green tea can protect human cellular DNA from ultraviolet and visible radiation-induced damage. Photodermatol Photoimmunol Photomed 2005, 21:15-22.
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Deana Ferreri, Ph.D., after finishing a B.S. in biomedical engineering, researched endothelial cell biology leading to a doctorate in biomedical science in 2008. While studying the cardiovascular system, Deana became interested in nutrition and lifestyle approaches to heart disease prevention. After graduating, she aimed to use her background in science to educate people about the powerful effects of food on health. Deana has been writing science-based content for DrFuhrman.com and assisting Dr. Fuhrman with literature research since 2009.
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