Can DNA testing make nutritional supplements safer? Some tests might not be up to snuff

One of the nation’s largest supplement manufacturers recently agreed to start DNA testing in the production of its products — part of an effort to assure consumers and policymakers who are increasingly skeptical that the ingredients listed on packages are accurate.

But the agreement between supplement manufacturer NBTY — the company behind brands such as Nature’s Bounty and Sundown Naturals — and the New York state attorney general’s office might not be sufficient, experts say.

Nutritional supplements, which are lightly regulated, have come under increasing scrutiny in recent years. Some are advertised as natural but contain pharmaceutical products. Others might not contain the ingredients on their label at all.

To address those concerns, the New York attorney general launched an investigation into herbal supplements over a year ago. The office sent four cease-and-desist letters to retailers — GNC, Target, Walgreens, and Walmart — demanding they stop selling certain products that did not contain DNA from the plants on the bottles’ labels.

Investigators have also tried to reach agreements with individual manufacturers.

In the latest case, NBTY said it would implement a system of “DNA barcoding” — a method used to identify which plant or animal a certain substance comes from. The protocol would cover a dozen ingredients over the next year, and within two years all ingredients. The attorney general’s office said that the final products would not be tested — rather, DNA barcoding would be used at different points along the supply chain.

But experts told STAT that in some cases, they would not expect herbal ingredient DNA to be present; in other cases, current testing methods might not find the substances even if they are present.

DNA barcoding is “antiquated technology,” said Steven Newmaster, a professor at the University of Guelph in Ontario, whose 2013 paper about the danger of herbal supplements helped spark the New York investigation.

The attorney general’s office disagreed with Newmaster’s assessment of the technology, calling it “a powerful and scientifically valid method for identifying potential fraud and contamination in the herbal supplement supply chain.” NBTY did not respond to requests for comment.

Newmaster said that his paper raised important red flags by identifying many problematic products, but that it wasn’t representative of all supplements.

After the paper was published, many companies started doing DNA testing, he said, but “none of that has been scientifically validated, so it just turned into a great big mess.”

In the middle of this mess, Newmaster said, he gets calls from companies who hired labs to test products or substances. A company will get the results of an analysis on a gingko leaf and, in confusion, call Newmaster: “This can’t be right. We sent you a leaf of ginkgo and you say there are five things in it. It’s just a leaf.”

Newmaster said that “the technology is not ready for commercial testing.”

Natalia Ivanova, a scientist at the Canadian Center for DNA Barcoding at the University of Guelph, agreed.

DNA barcoding isn’t the best way to test many supplements, Ivanova said, because it may be inaccurate or give useless information. For one thing, classical DNA barcoding works well to identify DNA from a single source, but not from a mixture. Often, supplements have many different substances in them, so classical DNA barcoding simply isn’t effective. More advanced tools are necessary.

But some advanced tools that people in the industry are using are too sensitive, Newmaster said. One of those is “next-generation sequencing,” which will pick up insignificant bits of DNA and make it look like a sample is contaminated.

“You’d be surprised what’s in your breakfast if you used that technology,” Newmaster said, including “all kinds of traces of bacteria and E. coli.”

Newmaster and Ivanova also said that it’s harder to find DNA in plant extracts than in raw plant material, like powdered leaves. To make extracts, you expose the plants to extreme heat or harsh chemicals, which break the DNA into small pieces. Newmaster said that technology can recover DNA from about 60 percent of the extracts they test.

Ivanova’s research supports this — in a PLOS ONE paper this year, she tested three different supplements, one that contained raw ginkgo material, and two that contained only gingko extract. DNA tests found nothing for the extracts, but different chemical tests confirmed that the gingko supplements did actually contain medicinal components.

Newmaster said that he’s been working with companies to help them better authenticate their products. Last week, he had a meeting with GNC. He’s also been in touch with supplement companies like Nature’s Way and Herbalife.

“My paper started a bit of a mess of this industry,” he said, “And I’m here to help.”