WESTCHESTER COUNTY, N.Y. -- New York State Attorney General Eric T. Schneiderman sent letters to four major retailers on Tuesday for allegedly selling store brand herbal supplement products that either could not be verified to contain the labeled substance, or were found to contain ingredients not listed on the labels.

The letters were sent to GNC, Target, Walmart and Walgreens for their sale of products including: Echinacea, Ginseng, St. John’s Wort and others.

The letters come as DNA testing, performed as part of an ongoing investigation by the Attorney General’s Office, allegedly shows that, overall, just 21 percent of the test results from store brand herbal supplements verified DNA from the plants listed on the products’ labels.

WalMart was the poorest performing retailer, with only four percent of the products showing DNA from the plants listed on the labels, the Attorney General said.

“This investigation makes one thing abundantly clear: the old adage ‘buyer beware’ may be especially true for consumers of herbal supplements,” Schneiderman said in a statement. "The DNA test results seem to confirm long-standing questions about the herbal supplement industry. Mislabeling, contamination, and false advertising are illegal."

The investigation looked at six different herbal supplements sold at the four major retail companies in thirteen regions across the state including Westchester County.

The testing revealed that all of the retailers were selling a large percentage of supplements for which modern DNA barcode technology could not detect the labeled botanical substance.

For a complete breakdown of the products listed from each store, click here and scroll toward the bottom of the page for a store-by-store breakdown.

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