Sean Moloughney12.02.09
Nine of 10 milk thistle supplements failed to meet quality standards, according to a recent test from ConsumerLab.com, White Plains, NY.
Two products failed to properly list the part of the milk thistle plant used—an 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 47-67%. 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 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. 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.
Two products failed to properly list the part of the milk thistle plant used—an 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 47-67%. 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 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. 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.