Green Tea Side Effects and Benefits
Green Tea, Camellia sinensis, Epigallocatechin Gallate (EGCG)

Green tea is different from black tea, that green tea is not fermented. The active ingredients
remain unaltered in the tea. Traditionally, green tea was used for digestion, depression,
immune enhancement, detoxification, and to prolong life. Green tea has been used in
conditions like: atherosclerosis, high cholesterol, weight loss, high triglycerides, hives immune
function and infection. Green tea is also believed to reduce the risks for certain cancers.

Green tea contains, minerals, vitamins, oils, caffeine and polyphenols (particularly the
epigallocatechin gallate (EGCG)). Probably, epigallocatechin gallate (EGCG) is green tea’s
key active ingredient. [1]



Most studies have shown that green tea can lower the total cholesterol levels and improve the
cholesterol profile [2-6] A study also demonstrated that green tea protected against damage to
LDL (“bad”) cholesterol caused by oxygen. [7-9]

In a recent study, mice were treated with high cholesterol food with or without catechins for 35
weeks. Elevated inflammatory factors, high plasma cholesterol levels, severe atherosclerosis,
liver and renal dysfunctions were found in the no catechin fed mice (i.e. the control mice), while
much milder conditions were observed in the catechin fed mice. [23]

Green tea may benefit people at risk of cancer.
Some tea leaves also contain compounds called Tea Polyphenols. Tea polyphenols are natural
plant antioxidants, which prevent damage caused by free radicals to DNA and other molecules.
Thus, they demonstrate cancer preventive properties by reducing abnormal cell growth and
inflammation. The purified component, epigallocatechin gallate (
EGCG), prevent colon cancer.
Recently, European scientists found EGCG prevents
cancer cells from growing by binding to a
specific enzyme. It appears to work in the same way as methotrexate.
[Scientists identify green
tea's cancer-fighter. Reuters, March 15, 2005].

A study of 19,749 men and 22,012 women led by Dr. Toru Naganuma, at Tohoku University
School, Japan suggests drinking 5 cups of green tea daily may lower the risk of developing
certain blood cancers. During 9 years of follow up, 157 blood, bone marrow, and lymph system
cancers developed in the study group. However, Dr. Toru Naganuma found that the overall risk
for blood cancers was 42 percent lower among study participants who drank 5 or more, versus
1 or fewer, cups of green tea daily. [A1]

In a study of over 219,000 men and women over the age of 40, researchers found that about
four in five of the participants drank green tea daily for a prolonged period of time. One third of
those -- notably women -- who drank five or more cups a day revealed a decreased risk of
developing gastric cancer. [A3]

In the gastrointestinal tract, green tea was found to activate intracellular antioxidants, inhibit
procarcinogen formation, and suppress angiogenesis and cancer cell proliferation. [20]
Studies on the preventive effect of green tea in esophageal cancer have produced inconsistent
results; however.several epidemiological, invitro and animal studies have shown that green tea
has a protective effect against lung cancer, breast cancer and prostate cancer. This preventive
potential of green tea against cancer is related to its active flavonoids - catechins.
Epigallocatechin 3-o-gallate, the major catechin in green tea, mediates diverse physiological
and pharmacological actions in bringing about the regression of the tumors and also lowers the
risk of nonmalignant cardiovascular proliferative diseases. These catechins exert diverse
physiological effects against cancers via several mechanisms, [10-16, 18]


Reactive oxygen species (superoxide, hydroxyl radical and nitric oxide) generation and
inflammation play important roles in the age-associated cognitive decline and neuronal loss in
neurodegenerative diseases such as Alzheimer's, Parkinson's and Huntington's diseases.
And, accumulation of iron at sites where the neurons die is one of the characteristics of these
diseases. Thus, researchers think that the accumulation of iron and reactive oxygen species
may lead to neuronal toxicity and the related diseases. Tea flavonoids (catechins) have been
reported to possess potent iron-chelating, radical-scavenging and anti-inflammatory activities.
Theoretically, it may help protect neuronal death and against the neurodegenerative diseases.

An ingredient in green tea, called epigallocatechin-3-gallate (EGCG) may help prevent
Alzheimer's disease. In a study of mice, EGCG decreased the production beta-amyloid. [24]


Green tea may help weight loss. A recent study in Netherlands has shown that green tea
reduced body weight, waist, respiratory quotient and body fat. The researchers explained that
High caffeine intake was associated with weight loss through thermogenesis and fat oxidation
and with suppressed leptin in women. In habitual low caffeine consumers, the green tea-
caffeine mixture improved weight maintenance, partly through thermogenesis and fat oxidation.
[22] However, more studies are needed to confirm this claim..

Green tea may benefit people at stress. A group also from Japan analyzed information on
daily green tea consumption, psychological distress as assessed by the Kessler 6-item
psychological distress scale, and other lifestyle factors. They found psychological distress
affected 2,774 (6.6 percent) of the respondents in the questionnaire. Respondents who
consumed more than five cups of green tea daily were less likely to experience psychological
distress than those who drank less than one cup daily. [A2]


Overdose of green tea may lead to side effects. Because green tea contains caffeine,
excessive consumption of green tea may lead to the side sides such as insomnia and anxiety.

Green tea is iron-chelating , thus, green tea extract may inhibit the absorption of non-heme iron
as much as 26%. [21] To avoid the side effects of green tea, never overdose ourselves with
green tea. Discuss with your doctor for the green tea side effects.

1. Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med 1992;21:334–50. 2. Kono S
et al. Green tea consumption and serum lipid profiles: A cross-sectional study in Northern Kyushu, Japan. Prev Med
1992;21:526–31. 3. Yamaguchi Y et al. Preventive effects of green tea extract on lipid abnormalities in serum, liver and
aorta of mice fed an atherogenic diet. Nip Yak Zas 1991;97:329–37. 4. Sagesaka-Mitane Y et al. Platelet aggregation
inhibitors in hot water extract of green tea. Chem Pharm Bull 1990;38:790–3. 5. Stensvold I et al. Tea consumption.
Relationship to cholesterol, blood pressure, and coronary and total mortality. Prev Med 1992;21:546–53. 6. Tsubono Y
et al Green tea intake in relation to serum lipid levels in middle-aged Japanese men and women. Ann Epidemiol 1997;7:
280–4. 7. Serafini M et al. In vivo antioxidant effect of green tea in man. Eur J Clin Nutr 1996;50:28–32. 8. Benzie IF et
al. Consumption of green tea causes rapid increase in plasma antioxidant power in humans. Nutr Cancer 1999;34:83–
7. 9. Sasazuki S et al. Relation between green tea consumption and severity of coronary atherosclerosis among
Japanese men and women. Ann Epidemiol 2000;10:401–8. 10. Suganuma M et al. Green tea and cancer
chemoprevention. Mutat Res 1999;428:339–44. 11. Weisberger JH et al. Tea, or tea and milk, inhibit mammary gland
and colon carcinogenesis in rats. Cancer Lett 1997;114:323–7. 12. Yang CS et al. Polyphenols as inhibitors of
carcinogenesis. Environ Health Perspect 1997;105(Suppl 4):971–6 [review]. 13. Menon LG et al. Anti-metastatic activity
of curcumin and catechin. Cancer Lett 1999;141:159–65. 14. Mukhtar H et al. Green tea in chemoprevention of cancer.
Toxicol Sci 1999;52(2 Suppl):111–7. 15. Katiyar SK et al. Tea consumption and cancer. World Rev Nutr Diet 1996;79:
154–84 [review]. 16. Kohlmeier L et al. Tea and cancer prevention: an evaluation of the epidemiologic literature. Nutr
Cancer 1997;27:1–13 [review]. 17. Mandel SA et al Multifunctional activities of green tea catechins in neuroprotection.
Modulation of cell survival genes, iron-dependent oxidative stress and PKC signaling pathway. Neurosignals. 2005;14(1-
2):46-60. 18. Doss MX et al, Trapping of growth factors by catechins: a possible therapeutical target for prevention of
proliferative diseases. J Nutr Biochem. 2005 May;16(5):259-66. 19. Crespy V et al A review of the health effects of green
tea catechins in in vivo animal models. J Nutr. 2004 Dec;134(12 Suppl):3431S-3440S. 20. Koo MW et al
Pharmacological effects of green tea on the gastrointestinal system. Eur J Pharmacol. 2004 Oct 1;500(1-3):177-85. 21.
Samman S et al. Green tea or rosemary extract added to foods reduces nonheme-iron absorption. Am J Clin Nutr 2001;
73:607–12. 22. Westerterp-Plantenga MS et al Body weight loss and weight maintenance in relation to habitual
caffeine intake and green tea supplementation. Obes Res. 2005 Jul;13(7):1195-204. 23. Suzuki J et al, Dietary
consumption of green tea catechins attenuate hyperlipidaemia-induced atherosclerosis and systemic organ damage in
mice. Acta Cardiol. 2005 Jun;60(3):271-6. 24. Green Tea Compound Stops Alzheimer's in Mice HealthDay Online
Publication, September 21, 2005 [A1] Green tea may curb risk of some cancers, Reuters, October 13, 2009 [A2] Green
tea reduces stress,, October 13, 2009 [A3] Drinking lots of green tea could ward off
stomach cancer in women, Relaxnews,, October 5, 2009
Studies suggest green tea may have benefit people at various aspects, as hthe green tea catechins
are anti-oxidative, anti-inflammatory, anti-carcinogenic, anti-arteriosclerotic and anti-bacterial.