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      • What is green tea?
      • How well does green tea work?
      • Is green tea safe?
      • Green tea conclusions
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How well does green tea work?

Biologic mechanism

A large number of in vitro and in vivo studies have demonstrated the anti-carcinogenic properties of green tea polyphenols by inducing apoptosis, cell-growth inhibition, cyclin kinase inhibition, and inhibition of urokinase (an enzyme crucial for cancer growth) (ref 1). The mechanism of action may include antioxidant and free-radical scavenging activity, and stimulation of detoxification systems through selective induction or modification of phase I and phase II metabolic enzymes.

Preventive efficacy

A Cochrane systematic review on green tea for cancer is at the protocol stage (ref 2). Thirty epidemiological studies, one meta-analysis, and two trials have been identified investigating the consumption of green tea and its association with the risk of developing cancer (ref 3-5).

Cancer prevention (3 studies)

A cohort study with different follow-up periods has found a negative association between green tea consumption with cancer incidence, especially among Japanese women drinking more than ten cups a day (ref 3,4). However, a study using a larger cohort of more than 38,000 people in Japan did find an association between green tea consumption and cancer incidence (ref 5).

Oesophageal cancer (4 studies)

Contradictory findings exist. A case-control study found that green tea drinking had a protective effect against oesophageal cancer among females (ref 6), while another case-control study showed a 39% decrease of risk of oesophageal cancer among alcohol drinkers, and 31% decrease among smokers (ref 7). A retrospective cohort study has demonstrated a positive association between drinking green tea and oesophageal cancer among males (ref 8). The urinary tea polyphenol epigallocatechin was inversly associated with cancer risk when gastric and oesophageal cancer subsites were combined (ref 9).

Stomach cancer (11 studies)

Eight epidemiological studies have found a reduction in the risk of stomach cancer from green tea consumption (ref 7,9-15). Three studies did not confirm an inverse association of green tea consumption and risk reduction of stomach cancer (ref 16-18).

Pancreatic cancer (4 studies)

Three case-control studies found an inverse association between drinking green tea and the risk of developing pancreatic cancer (ref 19-21). One case-controlled study has demonstrated a positive association between drinking five or more cups of green tea five daily with risk of pancreatic cancer (ref 22).

Liver cancer (1 study)

Drinking green tea has been shown to decrease the risk of developing liver cancer by 78% (odds ratio 0.25, 95% CI 0.11 to 0.57) among alcohol drinkers, and by 43% among smokers in one population-based case-control study (ref 7).

Biliary ducts cancer (1 study)

Statistical analysis has shown an increased risk of developing cancer of the biliary passages to be associated with green tea consumption according to the results of one retrospective cohort study (ref 8).

Colorectal cancer (3 studies)

Three case-control studies have found an association between drinking green tea and a decreased risk of developing colorectal cancer when those who did and did not drink green tea (ref 11,13,21).

Breast cancer (5 studies)

In a meta-analysis of two prospective cohorts with 35,004 Japanese women (ref 24), green tea intake was not associated with a lower risk of breast cancer (222 cases), and the multivariate relative risk for women drinking ≥5 cups compared with <1 cup per day was 0.84 (95% CI -0.57 to 1.24, p=0.69). One case-control study showed significantly reduced risk of breast cancer by regularly drinking high amounts of green tea (ref 25). However, a cohort study did not find an association of green tea intake with lower risk of breast cancer (ref 26). Another two cohort studies have shown decreased recurrence of breast cancer at stage I and II among patients who consume large amounts of green tea (≥3 cups per day) (ref 27,28).

Lung cancer (4 studies)

One randomized trial tested green tea, black tea, and water in 143 heavy smokers for four months (ref 29). An oxidative DNA damage indicator, 8-hydroxydeoxyguanosine in urine was significantly decreased after the intervention among those in the green tea group, but not in the black tea or water groups. A cohort study has found that green tea drinking might block cigarette-induced increase in sister-chromatid exchange rates, and thus could prevent lung cancer (ref 30). Consumption of green tea was found to be associated with a reduced risk of lung cancer among non-smoking women in one case-control study (ref 31). A phase I dose finding study showed the maximum tolerated dose of green tea extract as 3 g/m2 per day, and the dose-limiting toxicities were diarrhoea, nausea, and hypertension (ref 32).

Prostate cancer (1 study)

One case-control study showed that prostate cancer risk declined with increasing frequency, duration and quantity of green tea consumption (ref 33).

Urinary bladder cancer (1 study, 1 ongoing trial)

Reduced risk of urinary bladder cancer was found significantly for females who consumed matcha (a powdered green tea) in a case-control study (ref 34). A phase II randomized, double-blind, placebo-controlled, multicentre trial is undergoing in the US (ref 35).

Ovarian cancer (1 study)

A cohort study has found that increasing the consumption of green tea post-diagnosis may enhance epithelial ovarian survival (ref 36).

References

1. Anonymous. Green tea detailed scientific review. The University of Texas MD Anderson Cancer Center. http://www.mdanderson.org/departments/cimer/ accessed by 3 March 2005.
2. Schmidt K, Horneber M, Borrelli F, Ernst E. Green tea (Camellia sinensis) for the prevention of cancer. The Cochrane Database of Systematic Reviews 2004, Issue 4. Art. No.: CD005004. DOI:10.1002/14651858.CD005004.
3. Imai K, Suga K, Nakachi K. Cancer-preventive effects of drinking green tea among a Japanese population. Prev Med 1997;26(6):769-75.
4. Nakachi K, Matsuyama S, Miyake S, Suganuma M, Imai K. Preventive effects of drinking green tea on cancer and cardiovascular disease: epidemiological evidence for multiple targeting prevention. Biofactors 2000;13(1-4):49-54.
5. Nagano J, Kono S, Preston DL, Mabuchi K. A prospective study of green tea consumption and cancer incidence, Hiroshima and Nagasaki (Japan). Cancer Causes Control 2001;12(6):501-8.
6. Gao YT, McLaughlin JK, Blot WJ, Ji BT, Dai Q, Fraumeni JF Jr. Reduced risk of oesophageal cancer associated with green tea consumption. J Natl Cancer Inst 1994;86(11):855-8.
7. Mu NL, Zhou XF, Ding BG, Wang RH, Zhang ZF, Chen CW, et al. A case-control study on drinking green tea and decreasing risk of cancers in the alimentary canal among cigarette smokers and alcohol drinkers. Chinese J Epid 2003;24(3):192-5.
8. Hara N, Sakata K, Nagai M, Fujita Y, Hashimoto T, Yanagawa H. Statistical analyses on the pattern of food consumption and digestive-tract cancers in Japan. Nutr Cancer 1984;6(4):220-8.
9. Sun CL, Yuan JM, Lee MJ, Yang CS, Gao YT, Ross RK, Yu MC. Urinary tea polyphenols in relation to gastric and oesophageal cancers: a prospective study of men in Shanghai, China. Carcinogenesis 2002;23(9):1497-503.
10. Ji BT, Chow WH, Yang G, McLaughlin JK, Gao RN, Zheng W, Shu XO, Jin F, Fraumeni JF Jr, Gao YT. The influence of cigarette smoking, alcohol, and green tea consumption on the risk of carcinoma of the cardia and distal stomach in Shanghai, China. Cancer 1996;77(12):2449-57.
11. Kono S, Ikeda M, Tokudome S, Kuratsune M. A case-control study of gastric cancer and diet in northern Kyushu, Japan. Jpn J Cancer Res 1988;79(10):1067-74.
12. Sasazuki S, Inoue M, Hanaoka T, Yamamoto S, Sobue T, Tsugane S. Green tea consumption and subsequent risk of gastric cancer by subsite: the JPHC Study. Cancer Causes Control 2004;15(5):483-91.
13. Tajima K, Tominaga S. Dietary habits and gastro-intestinal cancers: a comparative case-control study of stomach and large intestinal cancers in Nagoya, Japan. Jpn J Cancer Res 1985;76(8):705-16.
14. Yu GP, Hsieh CC, Wang LY, Yu SZ, Li XL, Jin TH. Green-tea consumption and risk of stomach cancer: a population-based case-control study in Shanghai, China. Cancer Causes Control 1995;6(6):532-8.
15. Yu SZ, Zhang ZF, Yu GP, Zhu WD, Li YL, Wang MR, et al. Epidemiological study of the influence of drinking green tea on gastric cancer and chronic gastritis incidence. Chinese J Cancer 2001;11(1):41-5.
16. Hoshiyama Y, Kawaguchi T, Miura Y, Mizoue T, Tokui N, Yatsuya H, et al. A nested case-control study of stomach cancer in relation to green tea consumption in Japan. Br J Cancer 2004;90(1):135-8.
17. Hoshiyama Y, Kawaguchi T, Miura Y, Mizoue T, Tokui N, Yatsuya H, et al. A prospective study of stomach cancer death in relation to green tea consumption in Japan. Br J Cancer 2002;87(3):309-13.
18. Tsubono Y, Nishino Y, Komatsu S, Hsieh CC, Kanemura S, Tsuji I, Nakatsuka H, et al. Green tea and the risk of gastric cancer in Japan. N Engl J Med 2001;344(9):632-6.
19. Dai Q, Ji BT, Jin F, Xu M, Gao YT. Tobacco, alcohol and green tea consumption and pancreatic cancer: a population-based case-control study in urban Shanghai, China. Cancer 1996;16(1):5-10.
20. Goto R, Masuoka H, Yoshida K, Mori M, Miyake H. [A case control study of cancer of the pancreas] [in Japanese] Gan No Rinsho 1990;Spec No:344-50.
21. Ji BT, Chow WH, Hsing AW, McLaughlin JK, Dai Q, Gao YT, Blot WJ, Fraumeni JF Jr. Green tea consumption and the risk of pancreatic and colorectal cancers. Int J Cancer 1997;70(3):255-8.
22. Kato I, Tominaga S, Matsuura A, Yoshii Y, Shirai M, Kobayashi S. A comparative case-control study of colorectal cancer and adenoma. Jpn J Cancer Res 1990;81(11):1101-8.
23. Mizuno S, Watanabe S, Nakamura K, Omata M, Oguchi H, Ohashi K, et al. A multi-institute case-control study on the risk factors of developing pancreatic cancer. Jpn J Clin Oncol 1992;22(4):286-91.
24. Suzuki Y, Tsubono Y, Nakaya N, Suzuki Y, Koizumi Y, Tsuji I. Green tea and the risk of breast cancer: pooled analysis of two prospective studies in Japan. Br J Cancer 2004;90(7):1361-3.
25. Wu AH, Yu MC, Tseng CC, Hankin J, Pike MC. Green tea and risk of breast cancer in Asian Americans. Int J Cancer 2003;106(4):574-9.
26. Key TJ, Sharp GB, Appleby PN, Beral V, Goodman MT, Soda M, et al. Soya foods and breast cancer risk: a prospective study in Hiroshima and Nagasaki, Japan. Br J Cancer 1999;81(7):1248-56.
27. Inoue M, Tajima K, Mizutani M, Iwata H, Iwase T, Miura S, et al. Regular consumption of green tea and the risk of breast cancer recurrence: follow-up study from the Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC), Japan. Cancer Lett 2001;167(2):175-82.
28. Nakachi K, Suemasu K, Suga K, Takeo T, Imai K, Higashi Y. Influence of drinking green tea on breast cancer malignancy among Japanese patients. Jpn J Cancer Res 1998;89(3):254-61.
29. Hakim IA, Harris RB, Brown S, Chow HH, Wiseman S, Agarwal S, et al. Effect of increased tea consumption on oxidative DNA damage among smokers: a randomized controlled study. J Nutr 2003;133(10):3303S-09S
30. Shim JS, Kang MH, Kim YH, Roh JK, Roberts C, Lee IP. Chemopreventive effect of green tea (Camellia sinensis) among cigarette smokers. Cancer Epidemiol Biomarkers Prev 1995;4(4):387-91.
31. Zhong L, Goldberg MS, Gao YT, Hanley JA, Parent ME, Jin F. A population-based case-control study of lung cancer and green tea consumption among women living in Shanghai, China. Epidemiology 2001;12(6):695-700.
32. Laurie SA, Miller VA, Grant SC, Kris MG, Ng KK. Phase I study of green tea extract in patients with advanced lung cancer. Cancer Chemother Pharmacol 2005;55(1):33-8.
33. Jian L, Xie LP, Lee AH, Binns CW. Protective effect of green tea against prostate cancer: a case-control study in southeast China. Int J Cancer 2004;108(1):130-5.
34. Ohno Y, Aoki K, Obata K, Morrison AS. Case-control study of urinary bladder cancer in metropolitan Nagoya. Natl Cancer Inst Monogr 1985;69:229-34.
35. National Cancer Insitutte. Erlotinib and green tea extract (Polyphenon® E) in preventing cancer recurrence in former smokers who have undergone surgery for bladder cancer. http://clinicaltrials.gov/ct/action/GetStudy. accessed by 3 March2005.
36. Zhang M, Lee AH, Binns CW, Xie X. Green tea consumption enhances survival of epithelial ovarian cancer. Int J Cancer 2004;112(3):465-9.