Why Drink Green Tea?

June 16, 2016 by Deana Ferreri, Ph.D.


Green Tea

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
Green tea 70.20
White tea 42.45
Oolong tea 34.48
Decaffeinated green tea 26.05
Black tea

9.36

 

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

Cardiovascular health

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:

  • Reduces systolic and diastolic blood pressure
  • Reduces total and LDL cholesterol and LDL oxidation
  • Reduces fasting glucose and hemoglobin A1c
  • Improves endothelial function.15-20

Cancer prevention

Many anti-cancer effects have been attributed to green tea catechins:

  • Inhibiting proliferation and migration of cancer cells
  • Promoting apoptosis (programmed cell death) of cancer cells
  • Facilitating DNA repair
  • Angiogenesis inhibition
  • Inhibiting IGF-1 signaling
  • Anti-inflammatory effects21-31
  • Protection against UV-induced DNA damage in the skin22,32,33
  • Anti-estrogenic effects34,35

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.

 
References
  1. 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]

  2. Higdon J, Drake VJ: Tea. In An Evidence-Based Approach to Dietary Phytochemicals and Other Dietary Factors. Thieme; 2012: 42-51

  3. 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.

  4. Arab L, Liu W, Elashoff D. Green and black tea consumption and risk of stroke: a meta-analysis. Stroke 2009, 40:1786-1792.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  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.

  11.  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.

  12. Assuncao M, Andrade JP. Protective action of green tea catechins in neuronal mitochondria during aging. Front Biosci (Landmark Ed) 2015, 20:247-262.

  13.  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.

  14. 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.

  15.  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.

  16. 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.

  17. 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.

  18. 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.

  19.  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.

  20. 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.

  21. 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.

  22. Khan N, Mukhtar H. Cancer and metastasis: prevention and treatment by green tea. Cancer Metastasis Rev 2010, 29:435-445.

  23. Chen L, Zhang HY. Cancer preventive mechanisms of the green tea polyphenol (-)-epigallocatechin-3-gallate. Molecules 2007, 12:946-957.

  24. Singh BN, Shankar S, Srivastava RK. Green tea catechin, epigallocatechin-3-gallate (EGCG): mechanisms, perspectives and clinical applications. Biochem Pharmacol 2011, 82:1807-1821.

  25. 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.

  26. 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.

  27.  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.

  28. 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.

  29. 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.

  30. 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.

  31. 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.

  32. 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.

  33. 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.

  34. Fuhrman BJ, Schairer C, Gail MH, et al. Estrogen metabolism and risk of breast cancer in postmenopausal women. J Natl Cancer Inst 2012, 104:326-339.

  35. Monteiro R, Azevedo I, Calhau C. Modulation of aromatase activity by diet polyphenolic compounds. J Agric Food Chem 2006, 54:3535-3540.

  36. Chin JM, Merves ML, Goldberger BA, et al. Caffeine content of brewed teas. J Anal Toxicol 2008, 32:702-704.

  37. Astill C, Birch MR, Dacombe C, et al. Factors affecting the caffeine and polyphenol contents of black and green tea infusions. J Agric Food Chem 2001, 49:5340-5347.

  38. Venditti E, Bacchetti T, Tiano L, et al. Hot vs. cold water steeping of different teas: Do they affect antioxidant activity? Food Chemistry 2010, 119:1597-1604.

  39. U.S. Centers for Disease Control and Prevention. DHHS (NIOSH) Publication Number 86-114. Current Intelligence Bulletin 46. Methylene Chloride 1986 [http://www.cdc.gov/niosh/docs/86-114/]

  40. U.S. Centers for Disease Control and Prevention. The National Institute for Occupational Safety and Health (NIOSH). Ethyl acetate. 1994 [http://www.cdc.gov/niosh/idlh/141786.html]

  41. Lorenz M, Jochmann N, von Krosigk A, et al. Addition of milk prevents vascular protective effects of tea. Eur Heart J 2007, 28:219-223.

  42. Lorenz M, Stangl K, Stangl V. Vascular effects of tea are suppressed by soy milk. Atherosclerosis 2009, 206:31-32.

  43. Wagner M, Oehlmann J. Endocrine disruptors in bottled mineral water: total estrogenic burden and migration from plastic bottles. Environ Sci Pollut Res Int 2009, 16:278-286.

  44. U.S. Centers for Disease Control and Prevention. Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs): Epichlorohydrin [http://www.cdc.gov/niosh/idlh/106898.html]

  45. IFST issues statement on 3-MCPD. In Food Navigator, [http://www.foodnavigator.com/Science-Nutrition/IFST-issues-statement-on-3-MCPD]

  46. Orci T. Are Tea Bags Turning Us Into Plastic? In The Atlantic, 2013 [http://www.theatlantic.com/health/archive/2013/04/are-tea-bags-turning-us-into-plastic/274482/]

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.

 

Comments (0):

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Seastar

06/22/2016 04:25 PM

nice info. Please post info on roasted green tea. I prefer the flavor of roasted without grain added but wonder how much of the benefits is lost in roasting process.

Dr. Ferreri replies:

06/23/2016 05:13 PM

Unfortunately the USDA's flavonoid database doesn't contain information on roasted green tea. But it would be reasonable to think that some EGCG would be lost with that additional roasting step.

mschaeffer

06/23/2016 12:29 PM

Are there still health benefits to a second rendering of the used green tea leaves or should we just throw them away after the first brew? Quality green tea leaves are so expensive, it seems a shame not to use them a second time. One person said she even eats her green tea leaves after the second rendering. Or would it be more healthy just to make a new pot with fresh leaves?

Dr. Ferreri replies:

06/23/2016 05:21 PM

The paper I cited above (Astill, et al.) found that catechin extraction from a tea bag was about 80% after a 5 minute steep. It may, of course, be different with loose leaf tea, but it seems the second brew will be much lower in catechins than the first.

sarahslarson

07/06/2016 11:09 PM

Are there any health benefits to drinking green tea kombucha ?

veggielove replies:

09/20/2016 10:42 PM

Hello, did you get an answer to the GT Kombucha?

Dr. Ferreri replies:

09/21/2016 04:15 PM

Although there are a few in vitro and animal stuides reporting free radical scavenging activity of kombucha, there is not yet any evidence of significant health benefit in humans from drinking kombucha (made from green or black tea). Plus it contains added sugar.

This reply was last edited on 09/21/2016 04:15 PM

graceread

11/08/2016 06:40 AM

Can you give a few examples of the best green teas to drink, meaning the brand?  There are so many out there, I don't buy any because I don't know which one to purchase at the grocery store.

 

Dr. Ferreri replies:

11/10/2016 04:52 PM

No particular brand, but if you are looking to buy tea bags rather than loose tea, it's probably best to go with unbleached tea bags. As far as I know, Choice and The Republic of Tea use unbleached tea bags. 

Gavin5001

12/14/2016 04:57 PM

Is there any problem with ripping open a green tea bag and adding the leaves to a smoothie?

Dr. Ferreri replies:

12/14/2016 04:59 PM

No, no problem. It would probably be similar to drinking matcha, which is powdered green tea leaves.

Gavin5001 replies:

12/14/2016 05:03 PM

Thank you for your reply, Dr Ferreri. I appreciate it.

ellz

02/04/2017 03:50 PM

Hi,

I keep reading about the benefits of matcha.  It would seem to complement the nutritarian lifestyle. I cannot find any research to support the benefits. I just did a quick search and located this and one other article. Does Dr. F have any thoughts on matcha, types of matcha (some are flavored), and preparation?

Kindly, LFZ

Dr. Ferreri replies:

10/11/2017 05:13 PM

Matcha is powdered green tea and likely has similar benefits to brewed green tea, although there is not much research on it. 

Eokeefe112

04/21/2017 12:33 PM

HI,

I haven't seen a mention of coffee, is coffee restricted?  I drink green tea, but sometime it triggers an acid issue.  I am a coffee addict. My doctor told me it will be easier to stop taking drugs then coffee. I have slowed down a lot, but haven't been able to quit!  Thank you. Eokeefe

Dr. Ferreri replies:

10/11/2017 05:11 PM

Dr. Fuhrman recommends avoiding coffee or limiting to one cup per day. More info: https://www.drfuhrman.com/learn/library/articles/21/is-coffee-bad-or-good-for-you 

footey777

10/10/2017 08:17 AM

The caffeine in green tea is not beneficial, especially for people with osteoporosis ( caffeine causes the body to urinate more and out goes the calcium) or anxiety attacks.  

Dr. Ferreri replies:

10/11/2017 05:10 PM

The caffeine content of green teas is somewhat variable, but still quite low. Plus, decaffeinated green tea is widely available. 

zappo

06/02/2018 10:56 PM

What liquids are allowed and how much water should one drink

 

zappo

06/02/2018 10:56 PM

are smoothies okay made from kale, spinachm, oats, flax seeds, spirulina, chlorella, mangoes, berries and bananas