Analytical accuracy and reliability of commonly used nutritional supplements in prostate disease

We determine the analytical accuracy and reliability of commonly used nutritional supplements for prostate disease by comparing the amounts of active ingredients of several brands of vitamin E, vitamin D, selenium, lycopene and saw palmetto. We also compared the amounts of active compound in different lots of the same brand to determine the consistency of the manufacturing process.

Samples purchased at pharmacies and specialty stores were sent for independent chemical analysis. The measured dose was compared to the stated dose on the product label. Analysis of variance was performed to test for significance in interlot reliability.

Vitamin E (7 samples) and selenium (5) were within a range of -41% to +57% and -19% to +23% of the stated dosage, respectively. All vitamin D brands (4 samples) 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 less than 20% of the stated dosages. Lycopene brands were between -38% and +143% of stated dosages. Among the reliability assays 1 of 3 brands of vitamin E, 1 of 2 brands of selenium and 1 of 2 brands of saw palmetto demonstrated statistical differences in interlot dosage (p <0.0055, approximate 20% to 25% differences in dose). The 1 assayed form of vitamin D was reliable between lots.

Commonly used nutritional supplements for prostate disease vary widely in measured dose. Saw palmetto demonstrated tremendous variability with some samples containing virtually no active ingredients. In contrast, the more regulated substances we measured, such as vitamins and minerals, demonstrated less variation.