An ongoing investigation of popular herbal supplements subjected to DNA testing has found numerous store brand supplements aren’t what their labels claim to be, New York attorney general Eric Schneiderman said on Tuesday.

Schneiderman’s office has sent letters to GNC, Target, Walmart and Walgreen Co concerning supplements that either couldn’t be verified to contain the labeled substance or that contained ingredients not listed on the label. The products include echinacea, ginseng, St John’s wort, garlic, ginkgo biloba and saw palmetto.

Overall, just 21% of the test results from store brand herbal supplements verified DNA from the plants listed on the labels. The retailer with the poorest showing was Walmart. Only 4% of the Walmart products tested showed DNA from the plants listed on the labels.

“This investigation makes one thing abundantly clear: the old adage ‘buyer beware’ may be especially true for consumers of herbal supplements,” Schneiderman said.

Schneiderman asked the companies to provide detailed information on production, processing, testing and quality control for herbal supplements sold at their stores.

“We take these issues very seriously and as a precautionary measure, we are in the process of removing these products from our shelves as we review this matter further,” said a Walgreen spokesman, James Graham. “We intend to cooperate and work with the attorney general.”

Walmart spokesman Brian Nick said the company is immediately reaching out to suppliers of the products and will take appropriate action.

The investigation looked at six herbal supplements sold at stores across the state. Testing was performed by an expert in DNA barcoding technology, James Schulte II of Clarkson University in Potsdam, New York. The DNA tests were performed on three to four samples of each of the supplements purchased. Each sample was tested five times. Overall, 390 tests involving 78 samples were performed.

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

Contaminants identified include rice, beans, pine, citrus, asparagus, primrose, wheat, houseplant and wild carrot. In many cases, unlisted contaminants were the only plant material found in the product samples.

“We stand by the quality, purity and potency of all ingredients listed on the labels of our private label products,” said a GNC spokeswoman, Laura Brophy. “We will certainly cooperate with the attorney general’s office in all appropriate ways.”

Target didn’t initially respond to a request for comment.

Michael McGuffin, president of the American Herbal Products Association, which represents the herbal industry, called DNA testing “an emerging technology that has the potential to be useful in the future when it has been rigorously tested and validated”. He said identification of an herb through DNA testing must be confirmed with established analytical tools that herbal experts use, such as chromatography or microscopy.

The US Food and Drug Administration requires companies to verify their products are safe and properly labeled. But supplements aren’t subjected to the rigorous evaluation process used for drugs.

If a manufacturer fails to identify all the ingredients on an herbal product’s label, a consumer with allergies or who is taking medication for an unrelated illness could risk serious health issues every time a contaminated herbal supplement is ingested.

A DNA study conducted by the University of Guelph in 2013 also found contamination and substitution in herbal products in most of the products tested. One product labeled as St John’s wort, often used to treat depression, contained Senna alexandrina, a plant with laxative properties. One ginkgo product was contaminated with black walnut, which could endanger people with nut allergies.

A 2013 study from the Canadian Institutes of Health Research estimated there are about 65,000 dietary supplements on the market consumed by more than 150 million Americans.

http://www.theguardian.com/us-news/2015/feb/03/herbal-supplements-investigation-store-brand-products