Avoid supplement surprises

A look at the supplement industry and DNA barcoding

Industry analysts estimate that the size of the U.S. dietary supplement industry on the human side has grown to somewhere between $12 billion and $37 billion annually.1 While demand has increased steadily across the globe, so has competition between companies, prompting some to consider cost-cutting opportunities that can compromise quality and, once discovered, erode consumer confidence.

Fortunately, scrutiny of the industry has been mounting, especially since DNA barcoding, a type of genetic fingerprinting, has become more widely available.

DNA barcoding allows scientists to authenticate species in foodstuff, like imported fish,2 and herbal mixtures sold to consumers by the all-too-loosely-regulated supplement industry.3,4 

A turning point came in 2013 when researchers at the University of Guelph published a widely read paper detailing their findings of safety and quality problems in 44 herbal products. These mixtures had been obtained from 12 companies and spanned 30 different species of herbs. They also tested 50 leaf samples from 42 herbal species.

The authors found that nearly 60 percent of the products tested contained evidence of plant species that the manufacturer did not list on the label. Of the almost 50 percent of items that did include DNA from purported ingredients, a third of these products also showed evidence of undisclosed contaminants or fillers.

In several instances, the researchers found feverfew as a contaminant, an herb that could cause difficult to diagnose problems, especially if an individual was consuming feverfew unknowingly. Symptoms include nausea, vomiting, abdominal pain, diarrhea, flatulence, swelling and numbness of the oral cavity, and more. Sudden discontinuation of feverfew can lead to withdrawal syndromes, manifesting as rebound headaches, arthralgias and muscle pain.

Like many other herbs, feverfew interacts with medications metabolized by the liver, thereby producing unexpected outcomes from co-administered pharmaceuticals. Furthermore, feverfew may stimulate uterine contractions and, as such, is contraindicated for pregnant females due to the heightened risk of abortion.

The Guelph researchers also discovered many herbal substitutions in the compounds they examined.

For example, one product labeled as St. John’s wort contained no St. John’s wort DNA barcodes and only evidence of senna, an herbal laxative, leading to surprise outcomes for the consumer.

The authors made these recommendations: “We suggest that the herbal industry should embrace DNA barcoding for authenticating herbal products through testing of raw materials used in manufacturing products. The use of an SRM [standard reference manual] DNA herbal barcode library for testing bulk materials could provide a method for ‘best practices’ in the manufacturing of herbal products. This would provide consumers with safe, high-quality herbal products.”5 

More recently, investigators with the PBS show “Frontline” produced a damning exposé called “Supplements and Safety” (Jan. 19, 2016).6 

In this video, available for free at PBS here, a series of interviews show how little some manufacturers know about the science or quality of the products they are promoting and how much damage can ensue. It highlighted the “revolving door” between government regulators and industry and the extreme length to which concerned physicians and consumers need to go for the U.S. Food and Drug Administration to take action. It also showed that for change to occur, those outside of the FDA might need to be the ones to initiate it.

St. John’s Wort

Thankfully, change is taking place slowly. In September, New York’s attorney general, Eric T. Schneiderman, issued cease-and-desist letters to 13 makers of devil’s claw products marketed for arthritis.7 These letters demanded that the identified manufacturers stop selling, distributing or marketing “adulterated or misbranded devil’s claw supplements.”

Schneiderman based his pronouncements on findings from the New York Botanical Garden, where researchers employed DNA barcoding, as outlined in the Guelph paper, to assess the quality and quantity of ingredients in these supplements. In 16 out of 18 devil’s claw supplements, they found a less expensive substitute species for devil’s claw (i.e., Harpagophytum zeyheri instead of Harpagophytum procumbens procumbens), with different, and less desirable, active constituents.

As a result of Schneider-man’s inquiry, Nature’s Way, a long-standing herbal company, committed to a series of reforms related to its manufacture and labeling of devil’s claw. These would include employing DNA barcodes to ensure its products do not contain Harpagophytum zeyheri.

On a related matter, the attorney general directed four major retailers (Walmart, Target, Walgreen’s and GNC) “to halt the sale of certain herbal supplements following DNA barcode tests that failed to detect plant materials listed on the labels of the majority of products tested and also detected DNA associated with ingredients or contaminants not listed on the label.”

Reportedly, “a range of echinacea supplements” was found to “contain mostly rice and buttercup DNA, if they contained any plant material at all. Other store-brand supplements appeared to fare no better: Target’s valerian root showed traces of garlic and wild carrot but no valerian; Walgreens’ St. John’s wort consisted of garlic, rice and dracaena, a houseplant; Walmart’s ginkgo biloba had only dracaena, mustard, wheat and radish.”8 

By the next month, Schneiderman announced an “historic agreement with GNC to implement landmark reforms for herbal supplements. Under the agreement, GNC, one of the nation’s largest supplement retailers, will use DNA barcoding to authenticate plants used in supplements and adopt new testing standards to prevent contamination. The agreement also imposed reforms to improve transparency for consumers and to promote consumer safety.”

While DNA barcoding has its critics9 and ideally should be used in conjunction with other authentication methods,10 at least it’s a far cry from the current state of affairs in veterinary medicine. Although some groups like the National Animal Supplement Council11 are helping to monitor and improve manufacturing standards, we continue to see manufacturers sell products wherein they keep the amounts of ingredients, such as the herbal source of strychnine, a trade secret.12 


  1. Bradley J. NBJ: The US supplement industry is $37 billion, not $12 billion. Accessed at http://www.nutraingredients-usa.com/Markets/NBJ-The-US-supplement-industry-is-37-billion-not-12-billion on 02-25-16.
  2. Yan S, Lai G, Li L, et al. DNA barcoding reveals mislabeling of imported fish products in Nansha new port of Guangzhou, Guangdong province, China. Food Chem. 2016;202:116-119.
  3. Newmaster SG, Grguric M, Shanmughanandhan D, et al. DNA barcoding detects contamination and substitution in North American herbal products. BMC Medicine. 2013;11:222. Accessed at http://www.biomedcentral.com/content/pdf/1741-7015-11-222.pdf on 02-25-16.
  4. O’Connor A. Herbal supplements are often not what they seem. The New York Times. Nov. 3, 2013. Accessed at http://www.nytimes.com/2013/11/05/science/herbal-supplements-are-often-not-what-they-seem.html on 02-25-16.
  5. Newmaster SG, Grguric M, Shanmughanandhan D, et al. DNA barcoding detects contamination and substitution in North American herbal products. BMC Medicine. 2013;11:222. Accessed at http://www.biomedcentral.com/content/pdf/1741-7015-11-222.pdf on 02-25-16.
  6. PBS. Frontline: Supplements and Safety. Jan. 19, 2016. Accessed at http://www.pbs.org/wgbh/frontline/film/supplements-and-safety/ on 02-25-16.
  7. Attorney General Eric T. Schneiderman website. A.G. Schneiderman issues cease-and-desist letters to 13 makers of devil’s claw supplements marketed to arthritis sufferers. Accessed at http://www.ag.ny.gov/press-release/ag-schneiderman-issues-cease-and-desist-letters-13-makers-devil%E2%80%99s-claw-supplements on 02-25-16.
  8. Twilley N. How not to test a dietary supplement. The New Yorker. Feb. 10, 2015. Accessed at http://www.newyorker.com/tech/elements/dna-barcoding-new-york-dietary-supplement on 02-25-16.
  9. Collins RA and Cruickshank RH. The seven deadly sins of DNA barcoding. Molecular Ecology Resources. 2012; doi: 10.1111/1755-0998.12046.
  10. Jinbo U, Kato T, and Ito M. Current progress in DNA barcoding and future implications for entomology. Entomological Science. 2011;14:107-124.
  11. National Animal Supplement Council website: http://nasc.cc/
  12. Robinson N. Chinese herbs: selling strychnine. Veterinary Practice News. 3/25/14. Accessed at http://www.veterinarypracticenews.com/Medicine/Chinese-Herbs-Selling-Strychnine on 02-29-16.

Dr. Robinson, Dipl. ABMA, FAAMA, oversees complementary veterinary education at Colorado State University and is president and CEO of One-Health SIM Studio, a continuing education company in Fort Collins, Colo. Columnists’ opinions do not necessarily reflect those of Veterinary Practice News. 

Originally published in the April 2016 issue of Veterinary Practice News. Did you enjoy this article? Then subscribe today! 

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