Supplement reliability

Townsend Letter for Doctors and Patients,  Dec, 2004  by Robert A. Anderson

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Samples of supplements purchased at pharmacies and specialty stores were sent for independent chemical analysis. Vitamin E (7 samples) and selenium (5) were within a range of -41% to +57% and -19% to +23% of the stated dosage, respectively. Four vitamin D brands were within 15% of the stated dose. Saw palmetto (6 samples) were within a range -97% to +140% of the stated dosages with 3 containing <20% of the stated amounts. Lycopene brands were between -38% and +143% of stated dosages. Among the reliability assays, 1/3 brands of vitamin E, 1/2 brands of selenium and 1/2 brands of saw palmetto demonstrated statistical differences in interlot dosage (p<0.0055, approximate 20% to 25% differences in dose). The one assayed form of vitamin D was reliable between lots.

Feifer AH, Fleshner NE, Klotz L. Analytical accuracy and reliability of commonly used nutritional supplements in prostate disease. J Urol 2002 Jul; 168(1):150-4; discussion 154

COMMENT: Commonly used nutritional supplements for prostate disease varied widely in measured dose. Saw palmetto demonstrated very wide variability with some samples containing virtually no active ingredients. Vitamins and minerals demonstrated less variation. The issue of reliability and consistency in over-the-counter herbal and nutritional products commonly recommended for men's diseases continues to be something that deserves attention. And regulation does not guarantee consistency, either, witness the flap about inconsistent content in thyroxin preparations monitored by the FDA about four years ago. Practitioners should inquire about monitoring systems of supplement manufacturers and recommend to patients those whose screening and control procedures are in place and functioning.

COPYRIGHT 2004 The Townsend Letter Group
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