January 20, 2008

A January 15, 2008 article in the journal Clinical Cancer Research has sparked debate about the benefits and potential dangers of taking dietary supplements for general or prostate health or as a complementary therapy for prostate cancer. In the article, Dr. Shahrokh Shariat, chief resident in urology at the University of Texas Southwestern Medical Center, reported that two men developed a very aggressive prostate cancer within months of taking a product mislabelled as a dietary supplement. This product, which has since been removed from the market, was advertised as an aid to the development of stronger muscles and enhanced sexual performance. Upon analysis, however, it was found to contain the hormones testosterone and estradiol, a combination that laboratory tests found to be a potent stimulator of prostate cancer cells.

Although members of the nutritional supplement industry were quick to inform reporters that it was “a mistake” to call the product in question a “dietary supplement” and that the hormones it contained could be referred to more appropriately as “illegal drugs,” the incident re-enforces the old message: When it comes to complementary therapies, it is a case of buyer beware—and men should always inform their physicians of any over-the-counter drugs or supplements that they are taking, even when these products are advertised as “natural.”

Another issue, and one that has not received sufficient scientific study, is the effect on prostate health when men engage in some form of hormone replacement therapy or regularly take supplements advertised as boosting testosterone levels. Dr. Laurence Klotz, chief of the division of urology at Toronto’s Sunnybrook Health Science Centre, puts it this way: “Many men are on androgen replacement therapy or some kind of male hormone replacement, and there’s always been a concern this may stimulate the growth of prostate cancer cells.”

Still, some dietary supplements show promise, either as products that seem to relieve common prostate problems or as complementary therapies in the fight against prostate cancer.
For example, saw palmetto, derived from the berry of the saw palmetto tree, may be useful in treating the symptoms associated with benign prostatic hyperplasia (BPH) but not prostate cancer. Studies are conflicting, though. In 1998, research published in the Journal of the American Medical Association concluded that saw palmetto “produces similar improvement in urinary tract symptoms and urinary flow” as the drug finasteride “and was associated with fewer adverse treatment events.” (See the article “Saw palmetto extracts for treatment of benign prostatic hyperplasia.”) However, the results of a randomized trial, which were published in 2006 in the New England Journal of Medicine, found no evidence that saw palmetto had any more positive effect than a placebo when it came to improving “symptoms or objective measures of benign prostatic hyperplasia.” (See the article “Saw palmetto for benign prostatic hyperplasia.”)

Medical researchers warn, too, that saw palmetto (and other supplements advertised as improving prostate health) may suppress the levels of prostate-specific antigen (PSA) in the blood, which can interfere with your doctor’s ability to assess your PSA test results. For example, if your doctor is unaware that you are taking such a supplement, he or she might think, by looking at your PSA tests, that your cancer is under control, when it is not. Another excellent reason to inform your doctor of all the over-the-counter health products you take!

Selenium & Vitamin E
Two of the most promising dietary supplements in the fight against prostate cancer, selenium and vitamin E, are the subject of an international clinical trial. The Selenium and Vitamin E Cancer Prevention Trial (SELECT) has multiple sites across Canada, Puerto Rico, and the United States. It aims to determine whether one or both of these dietary supplements can prevent prostate cancer. Both supplements are antioxidants that might help control the cell damage that can lead to cancer. Both are being studied in relation to preventing prostate cancer because past research suggests the possibility of a connection.

A study published in 1996, which was designed to see whether selenium would help to prevent skin cancer, discovered that, although the male participants did not have a reduced rate of this cancer, those who took selenium for 6.5 years had approximately 60 percent fewer new cases of prostate cancer than men who took the placebo. (Click date to see an abstract of the 1996 study.) This result was confirmed by research published in 2002, which showed that men who took selenium for more than 7.5 years had about 52 percent fewer new cases of prostate cancer than men who took the placebo. (Click date to see the 2002 study.)

The possible connection between vitamin E and reducing the risk of prostate cancer was also discovered during research on a different cancer, lung cancer. In 1998, a study that followed the health of 29,133 male smokers in Finland, who were taking vitamin E to prevent lung cancer, discovered that these men had 32 percent fewer new cases of prostate cancer than men who took the placebo. (See an abstract of this study.)

For more information about SELECT, visit the trial's website, which is maintained by the Southwest Oncology Group.