Green Tea Kills Prostate Cancer Cells
PSA Rising, 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
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.
of green tea appears safe. There is some evidence that green tea
may prevent the occurrence of some forms of cancer ... Preliminary
evidence exists of the potential effectiveness of green tea as a
treatment of cancer. Further research into the effects of green
tea and some of its constituents would be worthwhile.
Task Force of Unconventional Therapies (Canada) 1998 (link below)
Green tea enzyme tNOX kills tumor cells December 14, 1998 Food Explorer "Tea Polyphenols"
Unconventional Therapies for Cancer; Green Tea
A review by Elizabeth Kaegi, MB, ChB, MSc, onsite at Canadian Medical Association.
Dr. E. Giovannucci at Harvard Medical School says: "Higher consumption of selenium and vitamin E, fructose/fruits, and tomatoes all have been associated with reduced occurrence of prostate cancer, but as yet their efficacy for prevention remains unproven." Five or more servings of fruit a day, according to a study that Dr. Giovannucci conducted, lowered the risk of prostate cancer by half.
In the group he studied, men who regularly avoided fruit while favoring foods high in calcium (ice-cream, cottage cheese, hard cheese and milk...) were at higher risk for prostate cancer.
Men who got 2,000 mg/day or more of calcium from food sources and supplements were almost three times as likely to have advanced prostate cancer, and 4.5 times as likely to have metastatic prostate cancer. That's the calcium in 6 glasses of milk.
This study looked at the eating habits and health outcomes of 47,781 male health professionals. All the men were free of cancer in 1986 when the study began. "Between 1986 and 1994, 1369 non-stage A1 and 423 advanced (extraprostatic) cases of prostate cancer were diagnosed."
Higher consumption of calcium, the researchers found, was related to advanced prostate cancer and metastatic prostate cancer. "Calcium from food sources and from supplements independently increased risk."
High fructose intake was related to a lower risk of advanced prostate cancer. "Fruit intake was inversely associated with risk of advanced prostate cancer...." Five or more servings of fruit a day made a measurable difference in risk of prostate cancer. "Non-fruit sources of fructose similarly predicted lower risk of advanced prostate cancer."
This study has been attacked by Dr. William Fair, a leading US urologist and a colon cancer survivor. Dr. Fair says that he himself takes 1,200 mg of calcium a day. Any idea that calcium in the diet encourages prostate cancer "flies in the face of all the evidence we have about vitamin D and prostate cancer, " Fair has said.
Giovannucci confirmed his results on repeating the study on a smaller group of men in Sweden. In 1999, though, a Dutch study of 58,279 men aged 55-69 followed for six years found "no associations" between prostate cancer and "consumption of fresh meat, fish, cheese and eggs. Positive trends in risk were found for consumption of cured meat and milk products ..... For calcium and protein intake, no associations were observed." But this study in the Netherlands did not compare fruit versus calcium consumption.
Vitamin D does protect men from prostate cancer. In the USA and many countries, milk is fortified with vitamin D. Even so, calcium in mik and other foods lowers the amount of usable vitamin D in the body. Eating several servings of fruit a day keeps the level of vitamin D raised.
A high circulating level of the biologically active form of vitamin D (1,25(OH)2 vitamin D [1,25(OH)2D) is known to inhibit formation of cancer in the prostate. Eating a diet high in meat and milk and low in fruit reduces the level of this anti-prostate cancer vitamin. "High intakes of calcium and phosphorus, largely from dairy products, lower circulating 1,25(OH)2D level, and sulfur-containing amino acids from animal protein lower blood pH, which also suppresses 1,25(OH)2D production."
On this evidence:
- Eating a lot of calcium in foods or supplements may suppress the body's production of the active form of vitamin D.
- Eating fruit stimulates the body to make the active form of vitamin D. Dietary fructose reduces plasma phosphate levels by 30 to 50% for more than 3 hours.
Fat in the diet might play a role in the development of prostate cancer -- and milk and meat are sources of fat. A recent study of men diagnosed with prostate cancer in Quebec, Canada found that the men who consumed the highest amount of saturated fat were significantly more likely to die of prostate cancer than of other causes.
The Harvard researchers say they took account of fat in calcium-rich foods and that still the balance between calcium and fructose was more important. "Our findings provide indirect evidence for a protective influence of high 1,25(OH)2D levels on prostate cancer," they say, "and support increased fruit consumption and avoidance of high calcium intake to reduce the risk of advanced prostate cancer.