Green tea made from tea plant leaves (Camellia sinensis) has been found to contain flavonoids, which are antioxidants in the polyphenol group that can inhibit cancer cell growth. The most effective flavonoid in cancer prevention is thought to be epigallocatechin-gallate (EGCG).
A review of research concerning the preventative effects of green tea on cancer in humans was conducted by European scientists1. They looked at studies that were available through December 2008 and selected fifty-one studies with 1.6 million participants to include in the review.
All of the studies chosen looked for a link between drinking green tea and cancer cell growth in humans. The majority of the studies focused on cancer of the digestive tract (27) and a few looked at breast, prostate, lung, ovarian, urinary and oral cancers.
Review Results
The reviewers concluded that the results of studies concerning digestive tract cancer were very contradictory. Results from studies on the other types of cancer were variable and generally failed to show a strong link between green tea consumption and a reduced risk of cancer development. Evidence was shown that green tea could reduce the risk of lung cancer (mostly in men) and urinary bladder cancer. But there was also information that green tea consumption could increase the risk of bladder cancer.
More Recent Review
Another review of academic literature conducted in July 2009 reported more than 1100 publications existed concerning the effect of polyphenols, the group of antioxidants that includes flavonoids, on cancer2. During the same time period the scientists also searched the PubMed database using the keywords “polyphenols – cancer – review” and received more than 320 relevant reviews.
This review identified that a prevalence of cancer research focused on the “targeted therapy approach”. They went on to search the PubMed database with the keywords “polyphenols – cancer – kinases” and found more than 130 results and half of them were published after 2003.
One aspect of the targeted therapy approach is targeting specific protein kinases to fight cancer.3 They inhibit tumor growth and prevent inflammation which is thought to cause some types of cancer. These results prove promising that scientists are moving forward in the quest to better understand the beneficial qualities of green tea when used medicinally.
It seems there was not enough strong evidence up until the end of 2008 to conclude that drinking green tea will prevent any type of cancer. However, since that time there have been numerous studies looking at the benefits of green tea with regard to cancer prevention and control.2 Although studies and reviews have produced mixed results, as scientists gain new information about the beneficial effects of green tea, research continues to be conducted. Scientific research is a process of elimination and advances in learning about are leading to continued study.2,3
1Green tea (Camellia sinensis) for the prevention of cancer. Boehm K, Borrelli F, Ernst E, Habacher G, Hung SK, Milazzo S, Horneber M. 2009. Cochrane Database System Rev. Jul 8;(3)
2Natural Polyphenols that Display Anticancer Properties through Inhibition of Kinase Activity.
Lamoral-Theys D, Pottier L, Dufrasne F, Nève J, Dubois J, Kornienko A, Kiss R, Ingrassia L. 2010. Curr Med Chem. 2010 Feb 16. [Epub ahead of print]
3Chemoprevention with phytochemicals targeting inducible nitric oxide synthase. Murakami A. 2009. Forum Nutr. 61:193-203. Epub 2009 Apr 7.
