Ask the Expert: Tea
Q: Is tea beneficial for cancer prevention?
A: Green Tea has been most recognized for having anti-cancer properties. Scientists have been researching green tea for decades. A recent study followed 69,000 Chinese women age 40-70 and found that the more green tea consumed, the lower the risk of developing colorectal cancer. The same effect has not been found for oral cancer, gastric cancer, and perhaps cancer in general. However, it appears that there is a lower mortality rate among regular green tea consumers. The health benefits of green tea stem from the antioxidant properties of catechins, or polyphenolic compounds that are especially high in green tea due its unique preparation. In fact, catechins make up 30% of the weight of dried leaves, the most prominent one being epigallocatechin-3-gallate (EGCG). It is known that antioxidant levels increase in the blood after green tea consumption, but the implications are unclear. A popular hypothesis is that antioxidants could prevent reactive oxygen molecules, known as free radicals, from damaging the body – a mechanism implicated in heart disease, cancer, and neurodegenerative diseases. More research is needed to understand green tea and its antioxidant activity in the human body. However, some clinical trials investigating green tea consumption by cancer patients found potential benefits that may prove promising.
Catechins can be found in many different types of teas, not just green tea, however the concentrations are inconsistent and variable.
Dufresne CJ, Farnworth ER. A review of latest research findings on the health promotion properties of tea. J. Nutri Biochem. 2001;12 (7):404-421.
Yang G, Shu X, Li H, Chow W, Ji B, Zhang X, et al. Prospective cohort study of green tea consumption and colorectal cancer risk in women. Cancer Epidemiol Biomarkers Prev. 2007;16(6):1219-1223.
Ide R, Fujino Y, Hoshiyama Y, Mizoue T, Kubo T, Pham TM, et al. A prospective study of green tea consumption and oral cancer incidence in Japan. Ann Epidemiol. 2007;17(10):821-826. Epub 2007 Jul 2.
Tsubono Y, Nishino Y, Komatsu S, Hsieh CC, Kanemura S, Tsuji I, et al. Green tea and the risk of gastric cancer in Japan. N Engl J Med. 2001;344(9):632-636.
Kuriyama S, Shimazu T, Ohmori K, Kikuchi N, Nakaya N, Nishino Y, et al. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA. 2006;296(10):1255-1265.
Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med. 1992;21(3):334-350.