Two products failed to properly list the part of the milk thistle plant used — a FDA requirement. Among the remaining supplements, only one contained the expected amount of silymarin compounds, which are believed to be the active constituents of milk thistle.
Studies suggest silymarin may be helpful in type 2 diabetes and, possibly, certain liver conditions.
While most products claimed that their milk thistle extracts were standardized to 80% silymarin, ConsumerLab.com found actual amounts to range from 47% to 67%.
Sales of milk thistle in the U.S. have climbed for several years, reaching $95 million in 2008 according to the latest figures from Nutrition Business Journal.
ConsumerLab.com’s Vice President for Research, Dr. William Obermeyer, a former scientist with the U.S. Food and Drug Administration (FDA), suggested supplement makers may be relying on non-specific tests, such as UV spectrophotometric analysis, that can falsely inflate a product’s silymarin content by counting other compounds that are not silymarin.
In contrast, ConsumerLab.com used a highly specific HPLC method to test the products.
Some ingredient suppliers offer both a higher priced and a lower priced milk thistle extract. The higher cost product is certified with the HPLC test, while the lower cost product is certified with the non-specific UV test.
The FDA does not set standards for the quality or testing of herbal supplements, so manufacturers may choose either form of milk thistle. Consumers normally have no way of knowing which form they purchase.
An abstract of the Product Review of Milk Thistle Supplements can be found here, however, the full review, including the full results, reviews, and comparisons of ten supplements selected by ConsumerLab.com is only available by subscription.
The Review provides information on how to choose and use these supplements. Brands included in report are 1Fast400, Enzymatic Therapy, Finest Natural, Jarrow Formulas, Natural Factors, Nature’s Plus, Nutrilite, Pharmex, Smart Basics (Vitacost.com), and Whole Foods.
ConsumerLab.com is one of my favorite web sites for evidence-based information on natural medications (herbs, vitamins, and supplements) and a leading provider of consumer information and independent evaluations of products that affect health and nutrition.
Reviews of other popular types of supplements are available from www.consumerlab.com. Subscription to ConsumerLab.com is available online here. The company is privately held and based in Westchester, New York. It has no ownership from, or interest in, companies that manufacture, distribute, or sell consumer products.
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