Compounds in Green Tea that are thought to help against cancer:
Catechins
A green tea leaf contains catechins, they are the components that give a bitter taste to the tea.
EGCG (epigallocatechin gallate) accounts for 10%-50% of the total green tea catechins. By virtue of its peculiar stereochemical structure, EGCG possesses much stronger anti-oxidant qualities than the other catechins found in green tea and plays an important role in preventing cancer and cardiovascular diseases. ECGC remove oxidised free radicals from the body which prevents damage to the cells and DNA. The anti oxidant properties of EGCG are believed to be 100 more times more effective than vitamin C and 25 times more effective than vitamin E. (http://www.herbs-tech.com/product/egcg.asp)
Flavonoids
Flavonoids are plant pigments; they are the brightly coloured chemical constituents found in most fresh fruits and vegetables. Flavonoids are essential for processing vitamin C and are needed to maintain capillary walls. They may aid in protecting against infection and deficiency can result in a tendency to bruise easily.
Health benefits
Reduces the risk of cancer
Acting components: Flavonoids and Catechins
How:
Carcinogens are cancer causing agents. Phytochemicals may prevent carcinogens from forming. Flavonoids are a type of phytochemical found in Green tea. Experimental studies have shown that tea and tea polyphenols have anti-carcinogenic properties against breast cancer.¹
Studies also suggest that ECGC may reduce the risk of cancer.²
A population-based, case-control study of breast cancer among Chinese, Japanese and Filipino women in Los Angeles County suggested an inverse link between Green tea intake and the development of breast cancer. ³ Similar study was done with women in Italy which showed a similar inverse link.⁴
Results from animal studies and possible cancer inhibitory mechanisms might be applicable to human cancer prevention. The results and possible applications are discussed in a study by C.S Yang et al. 2000.
‘Free radicals attack healthy cells, which changes their DNA, allowing tumors [sic] to grow. Antioxidants are substances that inhibit the oxidation process and act as protective agents. Antioxidants Research is underway to investigate the role of antioxidants in decreasing the risk of developing cancer. ’
(http://cancer.stanford.edu/information/nutritionAndCancer/reduceRisk/)
Catechins found in green tea are noted for their antioxidant properties.⁶
(http://www.herbs-tech.com/product/egcg.asp)
Studies
¹Can-Lan Sun , Jian-Min Yuan, Woon-Puay Koh and Mimi C. Yu Green tea, black tea and breast cancer risk: a meta-analysis of epidemiological studies Carcinogenesis 2006 27(7):1310-1315
² Maryam R. Sartippour, Zhi-Ming Shao, David Heber, Perrin Beatty, Liping Zhang, Canhui Liu, Lee Ellis, Wen Liu, Vay Liang Go and Mai N. Brooks Green Tea Inhibits Vascular Endothelial Growth Factor (VEGF) Induction in Human Breast Cancer Cells Journal of Nutrition. 2002 132:2307-2311
³Anna H. Wu , Mimi C. Yu , Chiu-Chen Tseng , Jean Hankin , Malcolm C. Pike. Green tea and risk of breast cancer in Asian Americans. International Journal of Cancer. Sept. 10 106(4) :574-579.
Cristina Bosetti, Luana Spertini, Maria Parpinel, Patrizia Gnagnarella, Pagona Lagiou, Eva Negri, Silvia Franceschi, Maurizio Montella, Julie Peterson, Johanna Dwyer, Attilio Giacosa and Carlo La Vecchia Flavonoids and breast cancer risk in Italy. Cancer Epidemiology Biomarkers & Prevention April 2005 Vol. 14, 805-808,
Chung S. Yang, Jee Y. Chung, Guang-yu Yang, Saranjit K. Chhabra and Mao-Jung Lee. Tea and tea polyphenols in cancer prevention. Journal of Nutrition. 2000;130:472S-478S..
⁶Balz Frei and Jane V. Higdon Antioxidant Activity of Tea Polyphenols In Vivo: Evidence from Animal Studies Journal of Nutrition October 2003 133:3275S-3284S
Restrains tumours
Acting component: Catechins (EGCG and ECG)
How:
EGCG stops the growth of tumours by inducing apoptosis¹ (process of cell self destruction), inhibiting cell-growth and disrupting the cell-cycle. ²
EGCG suppresses the growth of cancerous cells, ECG in some cases was found to be more effective as suppressing growth than EGCG. ³ Green tea contains both of these Catechins.
Angiogenesis is the growth of new blood vessels from pre-existing capillaries. This process is involved in the development of cancer. Angiogenesis is necessary for tumour growth, as it provides nutrients and oxygen for the growing tumour. A potential mechanism by which green tea may prevent cancer development is through the inhibition of angiogenesis.⁴
Researchers at the University of Murcia in Spain (UMU) and the John Innes Center (JIC) in Norwich have shown that EGCG prevents cancer cells from growing by binding to a specific enzyme.
-Research is published in the International Journal for Cancer Research.
Studies
¹ Rajesh L. Thangapazham, Anoop K. Singh, Anuj Sharma, James Warren, Jaya P. Gaddipati and Radha K. Maheshwari. Green tea polyphenols and its constituent epigallocatechin gallate inhibits proliferation of human breast cancer cells in vitro and in vivo. Cancer Lett. Epub March 3, 2006. Vergote D.; Cren-Olivé C.; Chopin V.; Toillon R-A.; Rolando C.; Hondermarck H.; Bourhis X.L. (-)-Epigallocatechin (GC) of green tea induces apoptosis of human breast cancer cells but not of their normal counterparts. Breast Cancer Res Treat. 2002 76, 3:195-201
²Vaqar M. Adhami, Nihal Ahmad and Hasan Mukhtar Molecular Targets for Green Tea in Prostate Cancer Prevention The Journal of Nutrition (July 2003) 133:2417S-2424S
N Ahmad, DK Feyes, AL Nieminen, R Agarwal and H Mukhtar Green tea constituent epigallocatechin-3-gallate and induction of apoptosis and cell cycle arrest in human carcinoma cells Journal Of The National Cancer Institute 1997, Vol 89, 1881-1886
Bigelow RL, Cardelli JA. The green tea catechins, (-)-Epigallocatechin-3-gallate (EGCG) and (-)-Epicatechin-3-gallate (ECG), inhibit HGF/Met signaling in immortalized and tumorigenic breast epithelial cells. Oncogene. 2006 25, 13:1922-30
³Mepur H. Ravindranath, Thiruverkadu S. Saravanan, Clarence C. Monteclaro, Naftali Presser, Xing Ye, Senthamil R. Selvan and Stanley Brosman Epicatechins Purified from Green Tea (Camellia sinensis) Differentially Suppress Growth of Gender-Dependent Human Cancer Cell Lines Evid Based Complement Alternat Med. 2006 Jun ;3:237-47
⁴Rodriguez SK, Guo W, Liu L, Band MA, Paulson EK, Meydani M. 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 2006;118(7):1635-44. Jian-Min Yuan , Woon-Puay Koh , Can-Lan Sun , Hin-Peng Lee and Mimi C. Yu . Green tea intake, ACE gene polymorphism and breast cancer risk among Chinese women in Singapore. Carcinogenesis. 2005 26, 8:1389-94,
Helps the success of cancer treatments
Acting Components: Catechin (EGCG)
How:
Radiation treatment for cancer can promote angiogenesis (the growth of new blood vessels from pre-existing capillaries providing nutrients and oxygen for the growing tumour) ECGC catechins have anti-angiogenic properties that could help to counteract this.¹
Studies
¹Annabi B, Lee YT, Martel C, Pilorget A, Bahary JP, Beliveau R Radiation induced-tubulogenesis in endothelial cells is antagonized by the antiangiogenic properties of green tea polyphenol (-) epigallocatechin-3-gallate. Journal of Cancer, Biology and Therapy 2003 Nov-Dec;2(6):642-9
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