Preliminary clinical trial finds that green tea antioxidants exert a striking slowing effect
Can green tea help retard the growth of prostate cancer? The answer to this question is key, because the wisdom of screening for and treating the generally slow-growing cancer remain mired in confusion and controversy. Doctors are not sure what to recommend to patients diagnosed with potential prostate cancer using the standard tests. For more on this, see “Prostate Testing and Treatment Dilemmas Persist,” in this issue. These uncertainties increase the importance of finding reliable dietary deterrents to prostate cancer occurrence, virulence, and progression. Prostate cancer rates are lowest in countries where men drink lots of green tea daily (Pandey M, Gupta S 2009; Clement Y 2009). (Studies have found no relationship, negative or positive, between drinking coffee and risk of prostate cancer.) In addition, whole green tea and the major antioxidants in green tea
—have shown anti-cancer promise in prior animal and human studies… and that promise just got a significant boost.
For example, studies in rodents show that green tea catechins significantly inhibit development of prostate cancer, especially when the cancer is in its early stages (Adhami VM et al. 2009).
Catechins (kat-eh-kins) are flavanol-type antioxidant compounds. In turn, flavanols belong to the large polyphenol family, which encompasses vitamin E and most of the antioxidants in fruits and vegetables. Catechins also occur in raw, non-Dutched cocoa.
Most epidemiological studies link green tea with reduced rates of prostate and breast cancer.
As an introduction to today’s news, it’s instructive to note the results of a year-long clinical trial from Italy, which showed that daily consumption of green tea catechins (GTCs) produced a ten-fold drop in the rate at which a pre-cancerous condition—high-grade prostate intraepithelial neoplasia—progressed to prostate cancer (Bettuzzi S et al. 2006).
As they wrote, “After one year, only one tumor was diagnosed among the 30 GTCs-treated men (incidence, approximately 3%), whereas nine cancers were found among the 30 placebo-treated men (incidence, 30%).”
New study adds to the promise of green tea vs. prostate cancer
Clinical results published by the American Association for Cancer Research show that the antioxidant compounds in green tea reduce blood markers proven to accurately predict the progression of prostate cancer.
Louisiana State University (LSU) researchers conducted the uncontrolled (open-label, single-arm) phase II clinical trial (McLarty J et al 2009).
They set out to determine the effects of green tea supplements on blood levels of “biomarker” compounds considered good indicators of the likelihood that prostate cancer will metastasize (spread to other organs) in patients diagnosed with the disease.
The study involved 26 men aged 41 to 72 years, diagnosed with prostate cancer and scheduled for radical prostatectomy.
The prognostic biomarkers in question are hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF).
The study also tested for prostate specific antigen (PSA), which does not reliably predict the existence or future course of prostate cancer.
The green tea supplement used in the trial (Polyphenon E) contained the flavanol-type polyphenol antioxidants found abundantly in green, black, and white tea, as well as in berries, other colorful fruits (prunes, plums, etc.) and cocoa.
The participants took four capsules of Polyphenon E daily for an average of 34.5 days, until the day before surgery.
The daily doses of Polyphenon E contained 800 mg of EGCG—often considered the most “bioactive” catechin in tea—and lesser amounts of other catechins, for a total of 1.3 grams of tea polyphenols. In terms of polyphenol content, this is the equivalent of drinking about 12 cups of green tea.
Following green tea supplementation, the men enjoyed significant reductions in blood levels of HGF, VEGF, PSA, and other cancer biomarkers, with some patients demonstrating reductions greater than 30 percent. Only a few minor reported side effects were reported, and the men’s liver function remained normal. William G. Nelson, V., M.D., Ph.D., of the Johns Hopkins Kimmel Cancer Center had these cogent comments:“Unfortunately, this trial was not a randomized trial, which would have been needed to be more sure that the observed changes were truly attributable to the green tea components and not to some other lifestyle change (better diet, taking vitamins, etc.) men undertook in preparation for surgery… [however] this trial is provocative enough to consider a more substantial randomized trial” (AACR 2009). The LSU researchers are currently conducting a comparable trial among patients with breast cancer, in collaboration with Columbia University. They also plan to conduct further studies to identify the factors that could explain why some patients responded more dramatically to Polyphenon E than others. Professor Cardelli suggested that additional controlled clinical trials should be done to see if combinations of different plant polyphenols are more effective than green tea catechins alone: “There is reasonably good evidence that many cancers are preventable, and our studies using plant-derived substances support the idea that plant compounds found in a healthy diet can play a role in preventing cancer development and progression” (AACR 2009). We’d say “yea” to that sentiment! From this perspective, it makes sense to drink green tea… or at least take supplements containing its key polyphenol compounds. Tea can’t hurt and may help! Sources
- Adhami VM, Siddiqui IA, Sarfaraz S, Khwaja SI, Hafeez BB, Ahmad N, Mukhtar H. Effective prostate cancer chemopreventive intervention with green tea polyphenols in the TRAMP model depends on the stage of the disease. Clin Cancer Res. 2009 Mar 15;15(6):1947-53. Epub 2009 Mar 10.
- American Association for Cancer Research (AACR). Green tea may affect prostate cancer progression. June 19, 2009. Accessed online at http://www.eurekalert.org/pub_releases/2009-06/aafc-gtm061509.php
- Bettuzzi S, Brausi M, Rizzi F, Castagnetti G, Peracchia G, Corti A. Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from a one-year proof-of-principle study. Cancer Res. 2006 Jan 15;66(2):1234-40.
- Clement Y. Can green tea do that? A literature review of the clinical evidence. Prev Med. 2009 May 22. [Epub ahead of print]
- McLarty J et al. Tea Polyphenols Decrease Serum Levels of Prostate-Specific Antigen, Hepatocyte Growth Factor, and Vascular Endothelial Growth Factor in Prostate Cancer Patients and Inhibit Production of Hepatocyte Growth Factor and Vascular Endothelial Growth Factor In vitro. Cancer Prev Res. First published online June 19, 2009 as doi:10.1158/1940-6207.CAPR-08-0167
Pandey M, Gupta S. Green tea and prostate cancer: from bench to clinic. Front Biosci (Elite Ed). 2009 Jun 1;1:13-25.