Health Benefits of Green Tea - Preventive Health Advisor

Here are 6 reasons why everyone should drink 4 cups of green tea daily starting now.

Health benefits of green tea (Camellia sinensis) are due to antioxidant polyphenol compounds known as catechins. Green tea has numerous health benefits cited in research. Green tea has been consumed for centuries by Asian countries and has been cited as generally safe, but adverse reports of green tea have been reported.

Health Benefits of Green Tea for Weight Loss

Green tea weight loss supplements have become popular because they reportedly assist people with their weight loss goals. Many weight loss products purchased over the counter may contain green tea among combinations of other supplements. Green tea weight loss supplements have both caffeine and the chemical EGCG. These two chemicals (part of the production of the supplement) may increase metabolism.

There have not been an extensive number of long-term studies using green tea weight loss supplements to document the effectiveness and side effects. Green tea contains less caffeine than coffee will not usually cause the same degree of anxiety or increase in heart rate. Green tea weight loss supplements also contain green tea catechins. These catechins are unfermented in green tea and in their natural state and are believed by some to suppress fat absorption from the diet.

Theanine is an amino acid found in green tea which has been found to induce relaxation and the release of dopamine which helps to provide a feeling of well-being. Theanine helps to reduce the effects of caffeine.

How Effective is Green Tea for Weight Loss?

Our review of the research has revealed that an average person can expect to lose at least 2-4 pounds of weight with consistent intake of about 4 cups of green tea daily over 8-12 weeks without changing any of the diet or activity level. This is supported by a randomized double-blind, controlled parallel multi-center trial included a treatment group with an intake of 583 mg catechin (equivalent of about 4-5 cups of green tea per day), while those in the control group had an intake of 96 mg catechin. Decreases in body weight, body mass index, body fat ratio, body fat mass, waist circumference, hip circumference, visceral fat area, and subcutaneous fat area were found to be greater in the catechin group than in the control group. Those in the treatment group experienced a loss of about 4 pounds after 12 weeks. (115)

Health Benefits of Green Tea Include Lowering Cholesterol

Kim A et al (111) evaluated the health benefits of green tea in 20 trials with a total of 1,415 subjects, green tea catechins in were taken in doses ranging from 145 to 3,000 mg/day for 3-24 weeks. The health benefits of green tea drinkers were seen in the reduction of total cholesterol by 5.46 mg/dL and LDL cholesterol by 5.30 mg/dL, as compared to controls. No significant changes in HDL cholesterol or triglycerides were found.

In a review and meta-analysis by Bogdanski P et al (112) found 14 randomized, controlled trials involving 1,136 subjects on the cholesterol related health benefits of green tea. were analyzed and results showed that consumption of green tea was associated with significant reductions in total cholesterol concentration (by 7.20 mg/dL) and LDL cholesterol concentration (by 2.19 mg/dL). No significant change in HDL cholesterol was found.

A beneficial effect of green tea (Camellia sinensis) taken as 250 mg capsules daily was demonstrated, with a significant reduction of total cholesterol and LDL cholesterol levels in an 8-week double-blind crossover study of 33 patients 21-71 years of age with dyslipidemias or an abnormal amount of lipids in the blood. Green tea supplementation resulted in a 3.9% reduction (p = 0.006) in total cholesterol concentrations and a 4.5% reduction (p = 0.026) in LDL cholesterol. The intake of green tea did not significantly influence HDL cholesterol, triglyceride, and Apo-B levels. (113)

Daily supplementation with 379 mg of green tea extract (GTE) lowered total cholesterol, LDL cholesterol and triglycerides. There was also an increase in HDL cholesterol observed. Following 3 months of treatment, LDL improved from 3.5 to 3.1 mmol/L, HDL from 1.2 to 1.4 mmol/L, triglycerides 1.4 to 1.1 mmol/L, total cholesterol 5.4 to 5.0 mmol/L, C-reactive protein from 3.4 to 2.5 mg/L and tumor necrosis factor 5.4 to 4.7 ng/L. (114)

Health Benefits of Green Tea Include a Lower Risk of Stroke

Shen L et al (48) analyzed fourteen studies (with a total of 513,804 participants) written from January 1966 to March 2012 to examine the relationship between green and black tea consumption and risk of stroke in a meta-analysis. They found that as tea consumption increased the risk of stroke decreased. Increasing tea consumption by 3 cups a day was associated with a 13% decrease in risk of ischemic stroke, but not cerebral hemorrhage and subarachnoid hemorrhage. When compared with infrequent or nondrinkers, there was a significant decrease in risk of ischemic stroke associated with drinking at least one cup of tea weekly, but the risk reduction was greatest among those drinking one to 2 cups of green or oolong tea daily (49).

Health Benefits of Green Tea May Include Lower Mortality From Cardiovascular Disease

Kuriyama, S et al of “the Ohsaki Study” (51) evaluated the health benefits of green tea for cardiovascular disease:

Researchers followed 40,530 Japanese adults up to 11 years.
Women who drank ≥ 5 cups/day of green tea had a 31% lower risk of dying from CVD and a 23% lower risk of mortality from all causes than women who drank <1 cup/day.
Women who drank 1 to 2 cups/day or 3 to 4 cups/day green tea had a 16% and 31% reduced risk of CVD, respectively.
Those who drank 1 to 2 cups/day or 3 to 4 cups/day green tea had a 2% and 18% reduced risk of all-cause mortality, respectively.
The protective effect of green tea was stronger in women than in men.
In men who drank ≥ 5 cups/day green tea their all-cause mortality risk fell by 12%.
Men who drank 1 to 2 cups/day or 3 to 4 cups/day green tea had a 7% and 5% reduced risk of all cause-mortality, respectively.

Sarin S et al (52) studied the health benefits of green tea using a Japanese insurance database for the relationship between green tea consumption and all-cause and disease-specific mortality. The population-based study included data on 40,530 Japanese adults aged 40 to 79 years. At baseline in 1994, all subjects were free of stroke, coronary heart disease, and cancer. All-cause mortality was assessed over 11 years’ follow-up and mortality from cardiovascular disease and cancer over 7 years’ follow-up. Especially for women, greater consumption of green tea was associated with lower all-cause mortality and mortality from cardiovascular disease. (52)

Kushiyama M. et al found that coffee, green tea, black tea, oolong tea consumption and cardiovascular disease risk (53):

Compared with non-tea drinkers, women consuming green tea at 1-6 cups/week, 1-2 cups/day, 3-5 cups/day and ≥ 6 cups/day had a 66%, 72%, 61%, and 58% reduced risk of coronary heart disease compared to non-tea drinkers.
Men drinking ≥ 1 cups/day of oolong tea benefited from a 61% reduced risk of CVD.
Individuals in the second highest quintile of total caffeine intake had a total CVD risk reduction of 38% in men and 22% in women.

Health Benefits of Green Tea May Include Lower Risk of Dementia

The Ohsaki Cohort Study (54) evaluated a population of over 13,000 Chinese adults. The risk of dementia was found to be 24% lower for those that consumed 5 cups of green tea or more compared to those who drank less than 1 cup.

6. Oral Health Benefits of Green Tea

Sarin, S. et al found that 2% green tea mouthwash rinsed for 1 minute twice daily was statistically significant in the reduction of both plaque and gingivitis after 28 days compared to placebo (52). A population study by Kushiyama M. et al used a questionaire to evaluate green tea consumption of 940 Japanese men 49 to 59 years old. Researchers found that a lower degree of periodontal disease was associated with an increasing number of cups of green tea consumption (53).

Green Tea Interactions and Adverse Reactions

When trying to obtain the health benefits of green tea, it is important to consult a physician. A physician can help to ensure that green tea will not interfere with any other medications, over the counter medications or health conditions.
Green tea has been quoted by multiple sources to contain a range of 120 to 160 mg of catechins per cup and an average of 23 mg of caffeine per cup (range of 11-48mg) but with high variability.
Preventive Health Advisor recommends that liver function tests be obtained at the discretion of a primary care provider for green tea consumption of 5 cups per day or greater at baseline due to high a variability in green tea catechin content.
Green tea extract is not recommended due to increased risk of hepatotoxicity with a higher concentration of catechins which it provides.
While drinking green tea, patients should be advised to avoid drugs metabolized by the liver such as acetaminophen.
According to Schönthal, the following adverse reactions have been reported (116):
- 34 case reports of hepatotoxicity, tremor, headache, pain, paresthesias, insomnia, palpitations, nausea, dysphagia, flatulence, and bloating.
- Green tea may reduce absorption of iron supplements, pseudoephedrine, theophylline, aminophylline, warfarin, codeine, atropine, ephedrine, carbinoxamine, dextromethorphan, Lomotil®, and Lonox.
- Green tea may increase the action of ephedrine, pseudoephedrine, theophylline, aminophylline, and reduce the effectiveness of adenosine, bortezomib, and sunitinib.
Green tea contains caffeine which is generally recognized as safe by the FDA and AMA but can be dangerous with adverse effects such as high bp, stroke, and arrythmias reported. If more than 4 cups of caffeinated beverages are consumed per day, it is prudent to seek physician and/or pharmacist approval of caffeine consumption with any medications or supplements.
When green tea is consumed in the form of whole leaves, or if it is steeped long enough to contain tannins, vitamin K is generally present in amounts significant enough to counteract the effects of warfarin (117,118), but if green tea is steeped for a short time, and the leaves are not consumed, green tea has very low concentrations of vitamin K (182).
Caution use of whole green tea leaves or powder in patients taking warfarin which may make achievement of therapeutic PTINR difficult. Vitamin K levels in coffee and tea was performed which revealed that vitamin K concentrations were about 0.03 μg/100 mL or less, and according to this source, brewed tea or coffee contains extremely small amounts of vitamin K and is not a dietary source (119).
Consumption of green tea at a dose of 4-6 cups daily for 6 months (480-960 mg of green tea catechins) has resulted in occasional episodes of toxic hepatitis, and the risk appeared to increase with chronic use (120). Caution use of green tea in patients with other forms of hepatitis, liver dysfunction, use of other medications cleared by the liver such as acetaminophen.
No adverse effect of green tea was found in a 12-week RCT but the study was fairly short term and both the study group and the control group had a low incidence of elevated liver function tests (115).

References for the Health Benefits of Green Tea

111.Kim A, Chiu A, Barone MK, Avino D, Wang F, Coleman CI, Phung OJ. Green tea catechins decrease total and low-density lipoprotein cholesterol: a systematic review and meta-analysis. J Am Diet Assoc. 2011 Nov;111(11):1720-9. http://www.ncbi.nlm.nih.gov/pubmed/22027055

112.Zheng XX, Xu YL, Li SH, Liu XX, Hui R, Huang XH. Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials. American Journal of Clinical Nutrition 2011; 94(2): 601-610. http://www.ncbi.nlm.nih.gov/pubmed/21715508

113.Batista Gde A, Cunha CL, Scartezini M, von der Heyde R, Bitencourt MG, Melo SF. Prospective double-blind crossover study of Camellia sinensis (green tea) in dyslipidemias. Arq Bras Cardiol. 2009 Aug;93(2):128-34. http://www.ncbi.nlm.nih.gov/pubmed/19838489

114.Bogdanski P, Suliburska J, Szulinska M, Stepien M, Pupek-Musialik D, Jablecka A. Green tea extract reduces blood pressure, inflammatory biomarkers, and oxidative stress and improves parameters associated with insulin resistance in obese, hypertensive patients. Nutr Res. 2012 Jun;32(6):421-7. http://www.ncbi.nlm.nih.gov/pubmed/22749178

115.Nagao T, Hase T, Tokimitsu I. A green tea extract high in catechins reduces body fat and cardiovascular risks in humans. Obesity (Silver Spring) 2007;15:1473–83. http://www.ncbi.nlm.nih.gov/pubmed/17557985

116.Schönthal AH. Adverse effects of concentrated green tea extracts. Mol Nutr Food Res. 2011 Jun;55(6):874-85. http://www.ncbi.nlm.nih.gov/pubmed/21538851

117.Taylor JR, Wilt VM. Probable antagonism of warfarin by green tea. Ann Pharmacother. 1999 Apr;33(4):426-8. http://www.ncbi.nlm.nih.gov/pubmed?term=10332534

118.Agency for Healthcare Research and Quality. Comparative Effectiveness of Dietary Supplement Versus No Dietary Supplement Use in Adults Taking Cardiovascular Drugs. April 2012. http://www.effectivehealthcare.ahrq.gov/ehc/products/223/596/DietarySupplement_Amended_Protocol_20110428.pdf

119.Booth SL, Madabushi HT, Davidson KW, Sadowski JA. Tea and coffee brews are not dietary sources of vitamin K-1 (phylloquinone). J Am Diet Assoc. 1995 Jan;95(1):82-3. http://www.ncbi.nlm.nih.gov/pubmed/7798585

120.Rohde J, Jacobsen C, Kromann-Andersen H. Toxic hepatitis triggered by green tea. [Article in Danish]. Ugeskr Laeger. 2011 Jan 17;173(3):205-6. http://www.ncbi.nlm.nih.gov/pubmed/21241631

46.Mineharu Y, Koizumi A, Wada Y, et al. Coffee, green tea, black tea and oolong tea consumption and risk of mortality from cardiovascular disease in Japanese men and women. J Epidemiol Community Health. 2011 Mar;65(3):230-40. Epub 2009 Dec 8. http://www.ncbi.nlm.nih.gov/pubmed/19996359

47.James JE. Critical review of dietary caffeine and blood pressure: a relationship that should be taken more seriously. Psychosom Med 2004; 66 (1): 63-71. http://www.ncbi.nlm.nih.gov/pubmed/14747639

48.Shen L, Song LG, Ma H, Jin CN, Wang JA, Xiang MX. Tea consumption and risk of stroke: a dose-response meta-analysis of prospective studies. J Zhejiang Univ Sci B. 2012 Aug;13(8):652-62. http://www.ncbi.nlm.nih.gov/pubmed/22843186

49.Liang W, Lee AH, Binns CW, Huang R, Hu D, Zhou Q. Tea consumption and ischemic stroke risk: a case-control study in southern China. Stroke. 2009 Jul;40(7):2480-5. Epub 2009 May 28. http://www.ncbi.nlm.nih.gov/pubmed/19478218

50.Lee M, Hong KS, Chang SC, Saver JL. Efficacy of homocysteine-lowering therapy with folic Acid in stroke prevention: a meta-analysis. Stroke. 2010 Jun;41(6):1205-12. http://www.ncbi.nlm.nih.gov/pubmed/20413740

51.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. http://www.ncbi.nlm.nih.gov/pubmed/16968850

52. Sarin S, Marya C, Nagpal R, Oberoi SS, Rekhi A. Preliminary Clinical Evidence of the Antiplaque, Antigingivitis Efficacy of a Mouthwash Containing 2% Green Tea – A Randomised Clinical Trial. Oral Health Prev Dent. 2015;13(3):197-203. doi: 10.3290/j.ohpd.a33447. http://www.ncbi.nlm.nih.gov/pubmed/25610918
53. Kushiyama M, Shimazaki Y, Murakami M, Yamashita Y. Relationship between intake of green tea and periodontal disease. J Periodontol. 2009 Mar;80(3):372-7. doi: 10.1902/jop.2009.080510 . http://www.ncbi.nlm.nih.gov/pubmed/19254120

54. Yasutake Tomata, Kemmyo Sugiyama, Yu Kaiho, Kenji Honkura, Takashi Watanabe, Shu Zhang, Yumi Sugawara, Ichiro Tsuji. Green Tea Consumption and the Risk of Incident Dementia in Elderly Japanese: the Ohsaki Cohort 2006 Study. Division of Epidemiology, Department of Health Informatics and Public Health, Tohoku University School of Public Health, Graduate School of Medicine, Sendai, Japan. Published Online: July 18, 2016.