Findings from a systematic review of preclinical experiments of green tea catechins’ (GTC) effects on breast cancer cells similarly suggested chemopreventive promise but only at very high concentrations “that are difficult to achieve in the clinical setting.”3

The authors called for development of more bioavailable formulations and testing of GTC as a potential adjuvant therapy to endocrine treatment for patients with breast cancer.

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Preclinical experiments suggest a possible synergy between GTCs and tamoxifen or raloxifene against breast cancer cells, possibly via both estrogen receptor-mediated and estrogen receptor-independent mechanisms.17 No such evidence has been reported for fulvestrant and GTC co-administration.

Evidence Against

Phase 1 clinical trials among patients with lung cancer failed to identify any objective tumor responses to green tea consumption.1 A meta-analysis conducted by Chinese researchers of published epidemiological studies found insufficient evidence to conclude that there is an association between green tea consumption and esophageal cancer, despite a subgroup analysis suggesting a possible risk reduction for women.18

Green tea consumption does not appear to affect the risk of pancreatic cancer.19

Take-home Conclusions

The evidence base is immature and equivocal. There is limited epidemiologic and lab-experiment evidence that green tea and green tea compounds are capable at high concentrations of affecting tumor biology. There is not, however, substantive clinical evidence that this potential translates to clinically meaningful cancer prevention or treatment benefits in humans.

References

  1. Fritz H, Seely D, Kennedy DA, Fernandes R, Cooley K, Fergusson D. Green tea and lung cancer: a systematic review. Integr Cancer Ther. 2013;12(1):7-24.
  2. Connors SK, Chornokur G, Kumar NB. New insights into the mechanisms of green tea catechins in the chemoprevention of prostate cancer. Nutr Cancer. 2012;64(1):4-22.
  3. Yiannakopoulou EC. Effect of green tea catechins on breast carcinogenesis: a systematic review of in-vitro and in-vivo experimental studies. Eur J Cancer Prev. 2014;23(2):84-9.
  4. Matsuo T, Miyata Y, Asai A, et al. Green tea polyphenol induces changes in cancer-related factors in an animal model of bladder cancer. PLoS One. 2017;12(1):e0171091.
  5. Kim YH, Won YS, Yang X, et al. Green tea catechin metabolites exert immunoregulatory effects on CD4(+) T cell and natural killer cell activities. J Agric Food Chem. 2016;64(18):3591-7.
  6. Thomas F, Holly JM, Persad R, Bahl A, Perks CM. Green tea extract (epigallocatechin-3-gallate) reduces efficacy of radiotherapy on prostate cancer cells. Urology. 2011;78:475.e21.
  7. Lee PM, Ng CF, Liu ZM, et al. Reduced prostate cancer risk with green tea and epigallocatechin 3-gallate intake among Hong Kong Chinese men. Prost Cancer Prost Dis. 2017 Apr 18. doi: 10.1038/pcan.2017.18 [Epub ahead of print]
  8. Guo YM, Zhi F, Chen P, et al. Green tea and the risk of prostate cancer: a systematic review and meta-analysis. Medicine. 2017;97(13):e6426. doi: 10.1097/MD.0000000000006426
  9. Jacob SA, Khan TM, Lee LH. The effect of green tea consumption on prostate cancer risk and progression: a systematic review. Nutr Cancer. 2017;69(3):353-64.
  10. Dostal AM, Samavat H, Bedell S, et al. The safety of green tea extract supplementation in postmenopausal women at risk for breast cancer: results of the Minnesota Green Tea Trial. Food Chem Toxicol. 2015;83:26-35.
  11. Choan E, Segal R, Jonker D, et al. A prospective clinical trial of green tea for hormone refractory prostate cancer: an evaluation of the complementary/alternative therapy approach. Urologic Oncol. 2005;108-13.
  12. Zhou Q, Li H, Zhou JG, Ma Y, Wu T, Ma H. Green tea, black tea consumption and risk of endometrial cancer: a systematic review and meta-analysis. Arch Gynecol Obstet. 2016;293(1):143-55.
  13. Huang YQ, Lu X, Min H, et al. Green tea and liver cancer risk: a meta-analysis of prospective cohort studies in Asian populations. Nutrition. 2016;32(1):3-8.
  14. Ni CX, Gong H, Liu Y, Qi Y, Jiang CL, Zhang JP. Green tea consumption and the risk of liver cancer: a meta-analysis. Nutr Cancer. 2017;69(2):211-20.
  15. Liu P, Zhang M, Xie X, Jin J, Holman CD. Green tea consumption and the glutathione S-transferases genetic polymorphisms on the risk of adult leukemia. Eur J Nutr. 2017;56(2):603-12.
  16. Naponelli V, Ramazzina I, Lenzi C, Bettuzzi S, Rizzi F. Green tea catechins for prostate cancer prevention: present achievements and future challenges. Antioxidants. 2017;6(2). doi: 10.3390/antiox6020026
  17. Yiannakopoulou EC. Interaction of green tea catechins with breast cancer endocrine treatment: a systematic review. Pharmacology. 2014;94:245-8.
  18. Sang LX, Chang B, Li XH, Jiang M. Green tea consumption and risk of esophageal cancer: a meta-analysis of published epidemiological studies. Nutr Cancer. 2013;65(6):802-12.
  19. Zeng JL, Li ZH, Wang ZC, Zhang HL. Green tea consumption and risk of pancreatic cancer: a meta-analysis. Nutrients. 2014;6(11):4640-50.

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Diet Fact Sheet General Oncology