Nutritional supplements commonly being used by consumers to reduce their risk of cancer can vary widely in their measured dose, according to new research presented at the annual meeting of the American Urological Association in Orlando.

The study, conducted by Toronto researchers, determined the analytical accuracy and reliability of popular supplements by comparing the amounts of vitamin E, vitamin D, selenium, lycopene and saw palmetto in different brands - purchased at local pharmacies and specialty stores.

During the blind study, samples were sent for independent analysis, and measured amounts were compared to the product label's stated dose. ANOVA analysis was also performed to determine inter-lot reliability.

"What we found was shocking," said Neil Fleshner, the study's lead researcher. "Some [brands] had hardly any, some only 15 percent of what they were purported to contain."

Analysis of the different brands of vitamin E fell within -41% to +57% of the stated dose; selenium within -19% to +23%; and lycopene between -38% and +143%. Saw palmetto samples fell between -97% and +140%. Only vitamin D samples demonstrated acceptable amounts.

In the inter-lot reliability assay, vitamin D had the only proven lot-to-lot reliability. Other supplements showed significant differences of approximately 20% to 25%.

"Non-responders to saw palmetto may benefit from a trial of an alternative brand," the researchers noted. But according to Fleshner, the study shows that in many cases, more is needed than just a brand switch. "It calls for some sort of regulation in the industry," he said.

SOURCE:
Annual Meeting of the American Urological Association, May 25, 2002, Orlando, Florida