Green tea is well known for its health benefits. Dr. Nagma Khan and Dr. Hasan Mukhtar of the University of Wisconsin provided a review of research on its effects on cancer growth. “Metastasis is the most deadly aspect of cancer and results from several interconnected processes including cell proliferation, angiogenesis, cell adhesion, migration, and invasion into the surrounding tissue,” they noted. Green tea can modulate the signaling pathways that enable metastasis.
Green tea contains polyphenolic compounds including epigallocatechin-3-gallate (EGCG). Khan and Mukhtar reported that EGCG has antioxidant activity 25 to 100 times more effective than vitamins C and E. They found the following research results for the effects of green tea on cancer metastasis in their literature review:
1. Breast cancer. In a study of 472 patients with breast cancer, it was found that women who drank more green tea had fewer axillary node metastases, fewer recurrences, and better results for progesterone and estrogen receptors. In cell cultures, EGCG reduced growth factors associated with metastasis.
2. Skin cancer. In hairless mice, green tea reduced the incidence, multiplicity, and growth of tumors induced by ultraviolet light. In lab studies of melanoma cells, ECGC reduced molecular and cellular characteristics of metastasis.
3. Lung cancer. Green tea catechins reduced the number of lung-metastatic colonies in a mouse model.
4. Liver cancer. EGCG and similar compounds reduced the proliferation and metastasis of human liver cancer cells in lab cultures.
5. Colon cancer. Tumors of human colon cancer implanted in mice showed inhibited growth in mice fed green tea extract.
6. Pancreatic cancer. Hamster models showed significantly lower tumor volumes in animals fed green tea extract.
In other review, Dr. Chung S. Yang of The State University of New Jersey and colleagues reported that tea constituents have antioxidative and anti-carcinogenic properties in numerous experiments. Studies in healthy volunteers showed that catechins can reduce plasma oxidized low density lipoprotein (LDL) and plasma hydrogen peroxide. Molecular studies showed that tea extracts can inhibit carcinogen-activating enzymes and increase the concentration of enzymes which detoxify carcinogens.
“Many case-control studies have shown that individuals who frequently consume tea had lower cancer risk,” Yang reported. “The antioxidative and anti-carcinogenic activities of tea polyphenols have been clearly demonstrated in animal models.” He recommended further human studies.
References:
1. Khan N et al, “Cancer and metastasis: Prevention and treatment by green tea”, Cancer Metastasis Rev. 2010 September; 29(3): 435-45. http://www.ncbi.nlm.nih.gov/pubmed/20714789
2. Yang CS et al, “Antioxidative and anti-carcinogenic activities of tea polyphenols”, Arch Toxicol. 2009 January; 83(1): 11. http://www.ncbi.nlm.nih.gov/pubmed/19002670
Reviewed August 10, 2011
by Michele Blacksberg R.N.
Edited by Jody Smith
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.