On Monday came more disturbing news about the dubious — and sometimes dangerous — practices in the dietary supplement industry. The New York state attorney general’s office ordered four major retailers — Target, GNC, Walmart and Walgreens — to immediately stop selling a number of their store-brand dietary supplements.

An investigation by that office had found that a large percentage of the supplements contain no trace of DNA from the herbs listed on their labels, while others contain ingredients not listed on their labels. That omission can put some people’s health at risk — those who have food allergies, for example, or who are taking a medication that might have an unwanted interaction with the supplement’s “hidden” ingredient.

“This investigation makes one thing abundantly clear: the old adage ‘buyer beware’ may be especially true for consumers of herbal supplements,” said New York’s Attorney General Eric Schneiderman in a statement released with the cease-and-desist letters sent to the retailers. “The DNA test results seem to confirm long-standing questions about the herbal supplement industry.”

The investigation was triggered by a 2013 New York Times report about adulteration, contamination and mislabeling in the herbal supplement industry.

Looking for DNA

Using DNA barcoding technology (a standard method of testing ingredients in food products), the investigation examined 24 different supplements sold at the four retailers (six from each company). The supplements were purchased in 13 different areas across New York State. Three to four samples of each supplement were tested, and each sample was tested five times.

The investigators found that 19 of the products contained none of the plant species listed on the labels. The missing plants were echinacea, gingko biloba, ginseng, saw palmetto, St. John’s wort, valerian root and garlic.

What those products contained instead were cheap fillers such as powdered rice, asparagus, pine, allium, daisy and houseplants. In addition, five of the supplements contained unlabeled substances — wheat and beans — that can be dangerous for people with allergies.

The retailer with the poorest showing was Walmart. Only 4 percent of its supplements tested contained the herbs listed on the products’ labels, and all of the supplements contained ingredients not on the labels.

Minnesota-headquartered Target had the fewest misleading products, but that isn’t anything the company can brag about. The investigation found that three out of six of Target’s “Up & Up” brand herbal supplements — St. John’s wort, gingko biloba and valerian root — tested negative for DNA from the labeled herb. Target’s supplements were also found to contain unlisted contaminants, including allium, powdered beans, asparagus, peas, wild carrots and saw palmetto.

On Tuesday, Target announced that it will stop selling the identified products at all of its stores and that it has asked its supplements vendor to investigate the issues raised by the New York state attorney general’s report.

Walmart said it will also stop selling the supplements cited in the report — but only in its New York stores. “Based on testing performed by our suppliers,” the company said, “we have not found any issues with the relevant products.”

A waste of money — and worse

I’ve written here many times in the past about the fraud and dangers associated with dietary supplements (including vitamin and mineral supplements) — for example, how Harvard University researchers found 27 supplements illegally contained powerful prescription drugs, including a drug that had been banned in the United States because of its association with an increased risk of heart attacks, and how research has tied some herbal and other dietary supplements to serious liver damage and an increased risk of cancer.

I’ve also written about how the $30 billion-a-year (in the U.S. alone) supplement industry has escaped any meaningful regulation thanks to the powerful help of congressional friends on both sides of the aisle.

Most consumers are unaware that companies do not have to prove a supplement is either safe or effective before it goes on the market. Only after people get ill — or die — can the U.S. Food and Drug Administration get the products off the shelves.

As a result of this lack of knowledge — and lack of accountability by the supplement industry — huge numbers of Americans (more than half, according to some surveys) continue to buy these products, swept up by dubious and almost always unsubstantiated health claims.

“The evidence for these herbs’ effectiveness is sketchy to begin with,” said David Schardt, a nutritionist at the Center for Science in the Public Interest, in the statement released by the New York state attorney general’s office. “But when the advertised herbs aren’t even in many of the products, it’s a sign that this loosely regulated industry is urgently in need of reform. Until then, and perhaps even after then, consumers should stop wasting their money.”

You can read more details about the actions taken Monday by the New York state attorney general office’s at the agency’s website.

(Full disclosure: Many years ago I worked as an editor at the Center for Science in the Public Interest.)