"A critical weekly review of important new research findings for health-conscious readers..."
By, Robert A. Wascher, MD, FACS
Last Updated: 07/05/2009
The information in this column is intended for informational purposes only, and does not constitute medical advice or recommendations by the author. Please consult with your physician before making any lifestyle or medication changes, or if you have any other concerns regarding your health.
PROSTATE CANCER & GREEN TEA Green tea has been consumed for thousands of years, and many claims regarding the health-promoting properties of this ancient beverage have been made over the millennia. However, we are just beginning to scratch the surface of green tea’s potential to aid in disease prevention and treatment through the use of modern laboratory and clinical research methods. While many of the fantastic claims being made for green tea are, doubtless, unlikely to be true, recent research has shown a surprising array of potentially beneficial effects associated with a group of compounds found in green tea. Green tea polyphenols, and epigallocatechins and epicatechins in particular, have especially piqued the interest of researchers looking at ways to improve the prevention and treatment of both cardiovascular disease and cancer. Unfortunately, most of the available research data for green polyphenols has been derived from low-powered dietary survey-based studies, or from laboratory studies of green tea extracts and their effects on cells artificially grown in culture dishes.
Now, a newly published clinical research study in the journal Cancer Prevention Research offers some intriguing insights into some potentially important clinical effects of green tea polyphenols in men with newly diagnosed prostate cancer. In this small pilot study, 26 men with newly diagnosed prostate cancer took daily supplements of green tea polyphenols while they were awaiting prostate cancer surgery (1.3 grams of polyphenols per day). At both the beginning and the end of this short-term study, blood was drawn to assess for tumor markers known to be associated with the stage and extent of prostate cancer (the study was concluded for these patients, individually, on the day that each underwent prostate cancer surgery). Additionally, cancer-associated fibroblast cells, which are often associated with multiple different types of cancer, and which are thought to secrete proteins that directly and indirectly increase tumor growth, were cultured in laboratory dishes, and then treated with green tea polyphenols. Changes in tumor-stimulating proteins from these prostate cancer-associated fibroblasts cells were then measured following polyphenol treatment.
Prostate-specific antigen (PSA), which is uniquely secreted by both normal and malignant prostate gland cells, is the most commonly used blood marker for prostate cancer. As prostate cancer progresses, PSA levels in the blood will rise in the vast majority of men with this disease. When prostate cancer is successfully treated, PSA levels will trend back towards normal levels. (Rising PSA levels following previous prostate cancer treatment almost always signify cancer recurrence.) Other important tumor-associated factors include vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). These proteins are known to stimulate the growth and spread of many types of cancer, including prostate cancer. Other known adverse tumor growth factors include insulin-like growth factor (IGF), and IGF binding protein. All of these tumor growth factors were measured in the blood samples collected from these 26 men, both at the beginning of this brief study and at its conclusion.
When all of the data was analyzed, some tantalizing results were discovered. Blood levels of PSA, VEGF, HGF, IGF and IGF binding protein were all significantly decreased following a brief period of dietary supplementation with green tea polyphenols. Additionally, VEGF and HGF secretion by prostate cancer-associated fibroblasts significantly decreased, as well, following treatment of these cultured cells with green tea polyphenols.
While this brief and small pilot does not provide any direct proof that dietary supplementation with green tea polyphenols can prevent prostate cancer, or improve survival in patients already diagnosed with prostate cancer, it does offer indirect evidence, based upon a decrease in prostate cancer-associated tumor markers, that green tea polyphenols may be able to inhibit prostate cancer cell growth, and not only in cancer cells growing in a laboratory culture dish, but also in a living, breathing human being with prostate cancer.
The obvious next step is to conduct several large, long-term, prospective, randomized, placebo-controlled clinical research trials to put the findings of this small but intriguing pilot study to the test. Fortunately, there are several such clinical trials already underway. Until the results of these clinical trials are known, however, it remains unclear if green tea polyphenols are capable of reducing the risk of prostate cancer (or any other type of cancer), or the risk of dying from a previously diagnosed prostate cancer, to any clinically significant degree. When the data from these larger prospective clinical research trials become available, I will certainly provide an update in this important area of cancer prevention and treatment research. Stay tuned!
Disclaimer: As always, my advice to readers is to seek the advice of your physicianbeforemaking any significant changes in medications, diet, or level of physical activity
Dr. Wascher is an oncologic surgeon, a professor of surgery, a widely published author, and the Physician-in-Chief for Surgical Oncology at the Kaiser Permanente healthcare system in Orange County, California
(Anticipated Publication Date: March 2010)
(Click above image for TV36 interview of Dr. Wascher)