TORONTO--Commonly used nutritional supplements for prostate disease vary widely in measured dose, according to an analysis conducted by researchers at the Toronto-Sunnybrook Regional Cancer Centre. Results of their study, which are available online (www.jurology.com), will be published in the July issue of The Journal of Urology (168, 1:150-4, 2002).
Researchers purchased samples of several brands of vitamin E, vitamin D, selenium, lycopene and saw palmetto at pharmacies and specialty stores, and sent them for independent chemical analysis. The measured dose was compared to the stated dose on the product label, and analysis of variance was performed to test for significance in interlot reliability.
Results indicated that all of the products varied in their specified dose and actual dose, although saw palmetto products fared the worst. The six saw palmetto samples were within a range of -97 percent to 140 percent of the stated dosages, with three containing less than 20 percent of the stated dosages. Lycopene samples didn't test much better. Lycopene brands were between -38 percent and 143 percent of stated dosages.
Researchers stated that the "more regulated substances," the vitamins and minerals, demonstrated less variation. The seven samples of vitamin E products and five samples of selenium products were within a range of -41 percent to 57 percent and -19 percent to 23 percent of the stated dosage, respectively. All four vitamin D brands were within 15 percent of the stated dose.
Additional results indicated that there were statistically significant differences in interlot dosages for some of the supplements. Among the reliability assays, one of three brands of vitamin E, one of two brands of selenium and one of two brands of saw palmetto demonstrated statistical differences in interlot dosages (approximately 20 percent to 25 percent differences in dose). The one assayed form of vitamin D was reliable between lots.
Researchers concluded that the commonly used nutritional supplements for prostate disease vary widely between labeled and measured dosages. They noted that saw palmetto demonstrated tremendous variability with some samples containing virtually no active ingredients, and, in contrast, the more regulated substances that were measured--such as vitamins and minerals--demonstrated less variation.