Green Tea

April 1998. Green tea contains compounds that kill prostate cancer cells. Most people in the USA and around the world drink black tea, if they drink tea at all. Only about a quarter of all tea drunk is green. Both kinds of tea leaves are from the same plant, the evergreen shrub Camellia sinens. Black tea is made from the withered, fermented leaves. The leaves sold as green tea have been steamed after picking, and are not fermented. This makes a difference. Green tea, evidence suggests, is more potent in anti-cancer ingredients.
      All plants contain compounds called polyphenols. These are especially high in tea, coffee, red grapes, kidney beans, raisins, prunes, and red wine. In December 1997 researchers at the Case Western Reserve University School of Medicine reported that an ingredient in the polyphenols in green tea kills cancer cells while sparing healthy cells.
      The researchers tested this ingredient, epigallocatechin-3-gallate, on human and mouse prostate cancer cells and on normal human skin cells. It caused apoptosis (programmed cell death) in cancer cells while leaving healthy cells unharmed. A report is in the Journal of the National Cancer Institute (Dec 17, 1997).
      The scientist in charge, Hasan Mukhtar, says the compound kills cancer cells by fragmenting their DNA - typical of apoptosis. Apoptosis happens all the time in a healthy body. Mukhtar says: "It is likely that this compound conveys a message to cancer cells through a highly ordered and well-regulated signal transduction pathway.... " The chemical messenger tells the cells "'You must commit suicide (programmed cell death) or I am going to kill you.' The cells then decide that instead of being murdered, they will commit suicide."
      Mukhtar believes study of green tea will lead to fuller understanding of the process of apoptosis. Researchers will try to decipher the molecular mechanism of green tea's protective effects. They will try to find out how to interfere with cancer development by adminstering purified polyphenolic derivatives, said Mukhtar. "Green tea appears to be potentially an ideal agent for chemoprevention." The investigators want to run clinical trials to see if indeed green tea can prevent cancer in humans.
      A nutritional trial for prostate cancer including green tea in the diet is ongoing at Memorial Sloan-Kettering Hospital in New York.

A search of "green tea" in National Cancer Institute's CANCERLIT® Bibliographic Database pulls in over 150 recent studies. Boil these down by entering "green tea prostate" in the search form. You'll reach listings of the CWRU study and, for now, three earlier studies. You can read the abstracts online.

Ahmad N, Feyes DK, Nieminen AL, Agarwal R, Mukhtar H: Green tea constituent epigallocatechin-3-gallate and induction of apoptosis and cell cycle arrest in human carcinoma cells. J Natl Cancer Inst; 89(24):1881-6 1997 "Green tea may protect against cancer by causing cell cycle arrest and inducing apoptosis [programed cell death]. It needs to be evaluated in human trials."

Carlin BI, Pretlow TG, Pretlow TP, Resnick MI: Green tea polyphenols inhibit growth of prostate cancer xenograft CWR22: implications for prostate cancer chemoprevention (Meeting abstract). Proc Annu Meet Am Assoc Cancer Res; 37:A1915 1996

Mohan RR, Khan SG, Agarwal R, Mukhtar H: Testosterone induces ornithine decarboxylase (ODC) activity and mRNA expression in human prostate carcinoma cell line LNCaP: inhibition by green tea (Meeting abstract). Proc Annu Meet Am Assoc Cancer Res; 36:A1633 1995

Liao S, Umekita Y, Guo J, Kokontis JM, Hipakka RA: Growth inhibition and regression of human prostate and breast tumors in athymic mice by tea epigallocatechin gallate. Cancer Lett; 96(2):239-43 1995

Don't want to wrestle with abstracts about "athymic mice"? Here's an ordinary language version ...

Bruce Carlin found that in mice high doses of green tea polyphenols prevent prostate cancer cells from growing. Tea had this effect even on cells exposed to testosterone, the male hormone, which normally stimulates prostate cancer. The effect depended on the dose of polyphenols.
      Not everyone finds green tea delicious, it's an acquired taste like any other. You might like it with splash of soy milk. Many pill forms are avialable for those who prefer. As part of a healthy diet together with exercise and medical checkups, green tea may give extra protection against cancer including prostate cancer. Whether anything in tea is powerful enough to stop established cancer from progressing (or to slow it down) is a different story, not yet unravelled.
      Evidence about the effects of diet on cancer has been gathered from broad analysis of global eating habits plus ultra-precise study of cells. The effects of food chemicals on cells are studied using advanced techniques, such as flow cytometry. A lot of work lies ahead to boil this down to what the patient wants to know, will it help me? Indications are encouraging, though.

Can It Do Harm?
You can't harm yourself by drinking green tea unless you take it scalding hot - bad for this kind of tea as well as for your mouth and throat. As for caffeine, green tea contains a lot less than coffee; and decaf green tea is available. If you're taking radiation therapy or chemotherapy, it is important to chask your oncologist about any antioxidants you are taking. Green tea would count as an antioxidant. Some beneficial substances can be counterproductive while you're on cancer therapy.
      Nothing suggests that green tea cures prostate cancer. Carlin's study used a strong concentration of active ingredients - about a hundred times what the Lipton company estimates is in one cup of tea. Carlin states: "Green tea is non-toxic, readily available, and inexpensive; it may be effective in the chemoprevention of prostate cancer." HUman studies are needed to see if indeed green tea extracts really can prevent cancer or slow the growth of existing tumors.

Food Explorer "Tea Polyphenols"
Unconventional Therapies for Cancer; Green Tea
A review by Elizabeth Kaegi, MB, ChB, MSc, onsite at Canadian Medical Association.
Back to Green Tea Page

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Updated December 17, 1998