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The Health Benefits of Green Tea

April 4, 2008 By Leave a Comment

green teaAccording to an ancient Chinese legend, a Chinese emperor discovered tea when leaves from a wild tea bush fell into a pot of water he was boiling.

Green tea originates from China, and is also now cultivated in India, Ceylon and Japan. It has recently become popular in Western countries where it has been more traditional to drink black teas.

The health benefits of green tea include decreasing breast cancer risk, reducing LDL cholesterol, and reduced risk of type 2 diabetes.

Health Benefits of Green Tea

  • LDL Cholesterol
    Epidemiologic studies suggest that drinking multiple cups of tea per day lowers LDL cholesterol.

    A double blind, placebo-controlled trial involving 240 men and women with high blood cholesterol concluded that theaflavin (polyphenol found in black tea) enriched green tea extract reduced LDL cholesterol.

    In a study involving obese subjects, green tea extract led to a reduction in LDL cholesterol.
  • Type 2 Diabetes
    Consumption of green tea has been associated with a reduced risk for type 2 diabetes, and people who drink green tea regularly are less likely to develop diabetes.

    The results of a study published in the August 2004 issue of BMC Pharmacology showed that green tea promoted glucose metabolism in the healthy human participants, providing evidence that green tea has an anti diabetes effect.
  • Cancer
    Experimental studies have shown that tea and tea polyphenols have anti-carcinogenic properties against breast cancer. A number of epidemiologic (population based) studies have examined the possible association between green tea intake and breast cancer development in humans. The results of these studies indicate a lower risk for breast cancer with green tea consumption.

    Women with low-activity genotype of the angiotensin-converting enzyme (ACE) gene have a reduced risk of breast cancer compared with those possessing high-activity ACE genotype. A study was conducted involving 297 incident breast cancer cases and 665 control subjects. There was no association between intake of green tea and risk of breast cancer among women with low-activity ACE genotype. Among women with high-activity ACE genotype, however, intake of green tea was associated with a statistically significant decrease in risk of breast cancer.

    EGCG is the catechin polyphenol in green tea that is thought to be responsible for it’s anti-cancer properties. EGCG is a powerful anti-oxidant, inhibiting the growth of cancer cells, with the ability to kill cancer cells without harming healthy tissue. EGCG accomplishes this by inhibiting the enzyme dihydrofolate reductase (DHFR), which cancer cells need to be able to grow, and which happens to be a target of anti-cancer drugs such as Methotrexate.

    • A recent study among smokers and non-smokers, those who did not drink green tea had a 5.16-fold increased risk of lung cancer compared with those who drank at least one cup of green tea per day. Among smokers, those who did not drink green tea at all had a 12.71-fold increased risk of lung cancer compared with those who drank at least one cup of green tea per day.
  • Weight Loss
    Green tea has thermogenic properties (a thermogenic increases the metabolism of the body’s fat), and promotes fat oxidation beyond that explained by its caffeine content. In a recent study of 60 obese subjects, it was concluded that green tea could reduce body weight by increasing energy expenditure and fat oxidation. In another study involving obese subjects, it was found that continuous ingestion of a green tea extract led to a reduction in body fat. The three ingredients in green tea that promote fat loss are catechins, caffeine and theanine that work by inhibiting the enzymes that digest triglycerides, which play an important role in metabolism as energy sources and transporters of dietary fat.

    In a 6-month study of rats that were fed green tea as the sole drinking beverage, it was found that green tea consumption decreases body mass.
  • Skin
    It has been suggested that a polyphenolic fraction from green tea may prevent UV radiation-induced skin cancer. There is however insufficient scientific research to back this theory up, and further studies are needed. In a double blind trial of green tea extracts in its role to treat aging skin, participants treated with a combination regimen of topical and oral green tea showed improvement in elastic tissue content.
  • Tooth Decay
    Several studies have demonstrated the anti-bacterial properties of green tea polyphenols are an effective agent against tooth decay.
  • Arthritis
    In vitro studies show that green tea consumption might benefit arthritis sufferers by reducing inflammation and slowing cartilage breakdown.

Quality and brewing time are important to derive optimal health benefits from green tea. Mediocre quality tea infused for less than 5 minutes will have polyphenol content 60 times less than a good quality tea brewed for more than 5 minutes.

EGCG Content in different green teas
EGCG concentration (% of leaf weight)
Tikuan yin 0.9%
Pou chong 0.9%
Dong ding 1%
Lung chin 1.5%
Meng ding 1.5%
Paimutan 2%
Yuzan 2%
Yunnan 2%
Matcha 2.8%
Gyokuro 2.9%
Pilo chun emperor 2.9%
Gyokuro #2 4.1%
Sencha #2 4.2%
Sencha #1 4.5%
Gyokuro #2 4.8%
Sencha-uchiyama 5.6%

1. Green tea should not be given to infants and young children.
2. EGCG might be unsafe for pregnant women

References:
1. Foods to Fight Cancer by Professor Richard Beliveau and Dr Denis Gingras.
2. Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J. 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 Dec;70(6):1040-5. PMID: 10584049.
3. Auvichayapat P, Prapochanung M, Tunkamnerdthai O, Sripanidkulchai BO, Auvichayapat N, Thinkhamrop B, Kunhasura S, Wongpratoom S, Sinawat S, Hongprapas P. Effectiveness of green tea on weight reduction in obese Thais: A randomized, controlled trial. Physiol Behav. 2008 Feb 27;93(3):486-91. Epub 2007 Oct 18. PMID: 18006026.
4. 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 Jun;15(6):1473-83. PMID: 17557985.
5. Maron DJ, Lu GP, Cai NS, Wu ZG, Li YH, Chen H, Zhu JQ, Jin XJ, Wouters BC, Zhao J. Cholesterol-lowering effect of a theaflavin-enriched green tea extract: a randomized controlled trial. Arch Intern Med. 2003 Jun 23;163(12):1448-53. PMID: 12824094.
6. Tsuneki H, Ishizuka M, Terasawa M, Wu JB, Sasaoka T, Kimura I. Effect of green tea on blood glucose levels and serum proteomic patterns in diabetic (db/db) mice and on glucose metabolism in healthy humans. BMC Pharmacol. 2004 Aug 26;4:18. PMID: 15331020.
7. Chiu AE, Chan JL, Kern DG, Kohler S, Rehmus WE, Kimball AB. Double-blinded, placebo-controlled trial of green tea extracts in the clinical and histologic appearance of photoaging skin. Dermatol Surg. 2005 Jul;31(7 Pt 2):855-60; discussion 860. PMID: 16029678.
8. You SQ. [Study on feasibility of Chinese green tea polyphenols (CTP) for preventing dental caries] Zhonghua Kou Qiang Yi Xue Za Zhi. 1993 Jul;28(4):197-9, 254. PMID: 8174399.
9. 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 Mar;132(3):341-6. PMID: 11880552.
10. Monteiro R, Assunção M, Andrade JP, Neves D, Calhau C, Azevedo I. Chronic green tea consumption decreases body mass, induces aromatase expression, and changes proliferation and apoptosis in adult male rat adipose tissue. J Nutr. 2008 Nov;138(11):2156-63. PMID: 18936213.
11. Sun CL, Yuan JM, Koh WP, Yu MC. Green tea, black tea and breast cancer risk: a meta-analysis of epidemiological studies. Carcinogenesis. 2006 Jul;27(7):1310-5. Epub 2005 Nov 25. PMID: 16311246.
12. Yuan JM, Koh WP, Sun CL, Lee HP, Yu MC. Green tea intake, ACE gene polymorphism and breast cancer risk among Chinese women in Singapore. Carcinogenesis. 2005 Aug;26(8):1389-94. Epub 2005 Mar 31. PMID: 15802301.
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