Green tea and prostate cancer

What researchers know

Can drinking green tea help fight prostate cancer?  Researchers have conducted both laboratory and human studies to find out. 

Some believe it is a powerful antioxidant.  Antioxidants are beneficial, because they may prevent the risk of cancer by blocking the actions of free radicals that have been associated with causing cell damage.

What makes it special?

Green tea is made from unfermented leaves and has a high concentration of powerful antioxidants called polyphenols, including catechins.

Steeping the leaves for five minutes has been shown to release over 80% of catechins. Tea catechins have been shown to inhibit cancer growth.

Laboratory studies: promising

  • Henning et al demonstrated that tumor volume was significantly decreased when green tea (GT) was administered to severe combined immunodeficiency (SCID) mice with androgen-dependent human LAPC4 prostate cancer cell subcutaneous xenografts
  • In studies where tumors were chemically created in mice, Adhami et al report that tumors decreased in size in those mice that were fed GT polyphenols

Researchers believe that these polyphenols work to prevent prostate cancer from spreading by:

  • Shutting down molecular pathways that are responsible for the growth and spread of tumor cells
  • Inhibiting blood vessels that contribute to tumor growth

More lab studies

  • Lee et al demonstrated that Epigallocatechin-3-gallate (EGCG) and a synthetic derivative — the peracetate of EGCG (EGCG-P) — inhibited tumor growth in mice and contributed to cell death in androgen-independent prostate cancer
  • Studies on concentrated green tea extracts have demonstrated the prevention of the growth of prostate cancer cells in test tubes

Human studies: mixed results

Recently, in a randomized clinical trial, Henning et al had 113 men with prostate cancer drink either six cups of brewed green tea, black tea, or water (control) a day before surgery for prostate cancer (radical prostatectomy).  There were no significant differences on the effects on prostate cancer biomarkers.

But when Fei et al analyzed various clinical studies, they determined that any kind of tea may have a protective factor in men with low-grade cancer.

Previous epidemiological studies comparing people who drink GT to those who don’t suggest that it helps prevent cancer. But other studies do not.

The challenge with epidemiological studies is that they can only show that a factor is associated with an outcome in men with prostate cancer. But they cannot prove a definite cause of the outcome.  There are other factors that can contribute to inconsistent results, including

  • Dietary habits
  • Environmental differences
  • Population differences

More green tea studies vary

  • In a study of 18,000 men in China, the number of tea drinkers who developed stomach or esophageal cancer was about 50% less than men who drank little
  • In another study, those who drank about 2 cups of GT a day and took an extract were able to reduce the size and growth of a precancerous oral plaque
  • In a large Japanese study where 49,920 men drank 5 cups of GT a day, Kurahashi et al suggested it may be associated with a decreased risk of advanced prostate cancer, but not localized prostate cancer
  • But a large study of 58,279 men and 62,573 women in the Netherlands demonstrated that there was no association between drinking tea and preventing stomach, colorectal, lung, and breast cancers

Chemotherapy warning

In studies, both green and black tea extracts stimulated genes that cause cells to be less responsive to chemotherapy drugs.

If your loved one is receiving chemotherapy, talk to his doctor about drinking teas or using any extracts.

Always check with a doctor or nutritionist before making any major dietary changes.

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References:

Adhami VM et al. Clin Cancer Res. 2009 Mar 15;15(6):1947-53.

Lee SC et al. Nutr Cancer.2008;60(4):483-91.

Kurahashi N et al. Am J Epidemiol.2008;167(1):71-7.

Trottier G,Boström P, Lawrentschuk L, Fleshner E. Nature Reviews Urology. 2000;7, 21-30.

Always consult a medical professional.

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