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Product Review: Milk Thistle Supplements |
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HOW PRODUCTS WERE EVALUATED:
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, catalogues, or multi-level marketing companies. Products were not accepted from manufacturers.
Testing Method:
Milk thistle products were tested for their total silymarin content (specifically dehydrosilybinin, isosilybinin A and B, silybinin A and B, silychristin and silydianin). All products were first analyzed in an independent laboratory for the silymarin constituents using the INA HPLC (High Performance Liquid Chromatography) assay. Products not passing this initial assay were tested in a second independent laboratory utilizing a similar HPLC assay.
Analyses for lead were made using Inductively Coupled Plasma/Mass Spectroscopy (ICP/MS).
Disintegration of non-chewable, non-capsule, non-enteric coated and non-time-release formulations was analyzed utilizing USP (United States Pharmacopeia) <2040> recommendations entitled "Disintegration and Dissolution of Nutritional Supplements."
The identities of the products were not disclosed to the laboratories performing the testing.
Passing Score: *
To achieve a "Pass" in the testing, a product had to:
- Meet all FDA requirements, including listing the following information in its labeling:
- Proper plant name (Milk thistle; Silybum marianum; or Silybum marianum (L.) Gaertn.);
- Part of the plant used (seed/fruit);
- Form of milk thistle used (e.g., seed powder, extract, or tincture);
- Amount of milk thistle or silymarin per pill or dose in grams (g) or milligrams (mg) [1 gram = 1,000 milligrams]
- Meet its label claim for total silymarin content, with a minimum of 1.5% silymarin for seed powder preparations (or a multiple of that for specified concentrations of seed powder) and a minimum of 70% silymarin (wt/wt) for dry extracts concentrates of unspecified concentration. Total silymarin was calculated as the sum of dehydrosilybinin, isosilybinin A and B, silybinin A and B, silychristin and silydianin.
- Not exceed California's Prop 65 levels for lead contamination in a recommended daily serving. [With few exceptions, this limit is 0.5 mcg. A product that exceeds the limit is required to display a lead warning if available for sale in California.]
- Meet recommended USP parameters for disintegration for vitamin supplements (excluding capsule, enteric coated, chewable and time-release products).
A "Pass" was based on meeting the above criteria in either the first or second rounds of testing.
* 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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