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Product Review: Resveratrol Supplements (Including Red Wine, Grape and Polygonum Sources) |
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How Products were Selected:
Products tested represent those commonly sold and/or available nationally in the U.S. ConsumerLab.com purchased products on the open market through retail stores, on-line retailers, and direct sales or multi-level marketing companies. Products were not accepted directly from manufacturers.
Testing Method:
Products were tested for amounts of resveratrol (specific isomers and total) as well as potential contamination with lead and cadmium. The products were also tested for their ability to disintegrate in solution (excluding chewable and time-release products).
All products were first analyzed in an independent laboratory by HPLC (High Performance Liquid Chromatography) assay to separate and determine the amounts of cis and trans resveratrol and cis and trans polydatin (a resveratrol glycoside, also known as piceid, which contains 58.7% resveratrol). Products not passing this initial assay were tested in a second independent laboratory utilizing a similar HPLC assay.
Analyses for lead and cadmium were made using Inductively Coupled Plasma/Mass Spectroscopy (ICP/MS).
Disintegration of non-chewable and non-time release formulations was analyzed utilizing USP (United States Pharmacopoeia) <2040> recommendations entitled "Disintegration and Dissolution of Nutritional Supplements."
All testing was conducted by independent laboratories to which the identities of the products were not disclosed.
Passing Score: *
To pass, a product had to:
- Contain at least 100% and no more than 150% of its claimed amount of total resveratrol and specific forms of resveratrol, Total resveratrol was calculated as the sum of cis and trans resveratrol plus 58.7% of the sum of cis and trans polydatin.
- Not exceed California Prop 65 levels for lead contamination in a recommended daily serving and, in no event, exceed 2 mcg of lead in a recommended daily serving.
- Contain less than 0.3 parts per million (or micrograms per gram) of cadmium for dried raw herb (World Health Organization, Quality Control Methods for Medicinal Plant Material, proposed guidelines, 1998) or less than 0.1 parts per million for extracts. The lower concentration standard for extracts reflects the ability to remove heavy metals such as cadmium during the extraction process.
- Meet recommended USP parameters for disintegration for dietary supplements (excluding capsule, enteric coated, chewable and time-release products).
- Product must meet all FDA labeling requirements.
A "Pass" was based on meeting the above criteria in either the first or second rounds of testing. Re-testing was performed in a second independent laboratory.
* Passing scores allow for specific margins of technical error associated with each analysis. ConsumerLab.com reserves the right to disqualify a product at any time from passing its testing if it considers such product to present a safety risk or to provide misleading or inaccurate information in its labeling.
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