A recent study by researchers at UT Southwestern Medical Center concludes that hormonal components in over-the-counter dietary supplements may actually accelerate the progression of prostate cancer, at the same time decreasing the effectiveness of anti-cancer drugs.
The study, published in the January 11, 2008 issue of Clinical Cancer Research, strongly advises patients to tell their doctor if they are taking any herbal or hormonal dietary supplements. It is also recommended that the use of such supplements is routinely documented as part of the patient’s health assessment.
"Physicians need to ask their patients not only about the prescription drugs they may be taking, but—perhaps even more importantly—about the over-the-counter drugs and supplements, which may have a profound impact on certain health conditions," said Dr. Claus Roehrborn, chairman of urology at UT Southwestern and one of the study’s authors.
The research commenced when two UT Southwestern patients developed aggressive prostate cancer mere months after starting daily use of the same dietary supplement—one for muscular development, the other for sexual enhancement. When Dr. Roehrborn and Dr.Shariat, a resident in urology and the study’s lead author, and their colleagues analyzed the product (not named in the study) they found that the label listed ingredients not present, misrepresented the concentrations of the ingredients that were present, and did not list all the steroid hormones in the product.
Hormone analysis showed the presence of testosterone and estradiol, a sex hormone. Testing of the product’s effect on human prostate cancer-cell lines revealed that the product was a more potent stimulator of cancer-cell growth than testosterone. Use of the anti-cancer drug bicalutamide, in increasing concentrations, proved ineffective.
"Bicalutamide is an oral nonsteroidal anti-androgen used to treat prostate cancer," Dr. Shariat said. "The fact that this supplement caused the drug to be less effective is very troubling." The researchers filed an adverse event report with the Food and Drug Administration, which in turn issued a warning letter to the manufacturer, who withdrew the product from the market.
"Unlike prescription and over-the-counter drugs, the law does not require nutritional supplements to undergo pre-market approval for safety and efficacy," Dr. Shariat said. "The current FDA regulatory system provides little oversight or assurances that dietary supplements will have predictable pharmacological effects or even that product labels provide accurate information for consumers."
It is estimated that 42% – 69% of U.S. adults use dietary supplements, at an estimated cost of $34 billion. People often use supplements in the belief that these natural products are safe and drug-free. The sale of androgenic steroids meanwhile is increasing exponentionally, with 2004 sales U.S. expenditures on testosterone supplements totalling an estimated $425 million.
"Given that testosterone supplements are in high demand, there is significant concern that supplements, in addition to the one we evaluated, may pose an urgent human health risk," Dr. Shariat said.
Researchers from Baylor College of Medicine in Houston also contributed to the research.
"The current FDA regulatory system provides little oversight or assurances that dietary supplements will have predictable pharmacological effects or even that product labels provide accurate information for consumers."