Am Fam Physician. 2002;66(7):1299
Complementary and alternative health treatments are becoming more common; almost one half of men with or at high risk for prostate cancer are using some form of nutritional supplement for the condition. In this market, saw palmetto is one of the most common herbal agents sold in the United States. Because these supplements are considered foods, manufacturing quality control standards and efficacy are not regulated rigorously. Feifer and associates tested the reliability of the contents of commonly used supplements for prostate disease.
Multiple brand samples of vitamin E, vitamin D, selenium, lycopene, and saw palmetto underwent chemical analysis by an independent laboratory blinded to the specific doses and brand names. Of the seven brands of vitamin E, only three were within 15 percent of the stated dose, and three were above or below the stated dose by 40 percent. Among the five brands of selenium, two were within 15 percent of the stated dose. Of the six brands of saw palmetto, there was a variation from −97 to +140 percent of the stated doses, with three of the samples containing less than 20 percent of the stated dose. Of the six brands of lycopene, two were within 15 percent of the stated dose. Standardization of vitamin D was better, with all four samples being within 15 percent of the stated dose. Interlot reliability testing demonstrated variations of greater than 20 percent among vitamin E, selenium, and saw palmetto tablets from the same manufacturer.
The authors conclude that supplements commonly used for prostate disease often contain more or less than the stated dose. Variation and unreliability was greatest for saw palmetto compared with the other preparations, which included more closely regulated vitamins and minerals. Some samples of saw palmetto had virtually no active ingredient.