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DNA testing is all the rage these days. If you’re sufficiently curious and you have enough money, you can use DNA technologies for everything from tracking down your primitive ancestors to measuring your risk for cancer or even determining how you’ll respond to certain medications. DNA testing has made an impact on the supplement industry, too. About a year ago, researchers from the University of Guelph in Ontario, Canada, used a special technique called DNA barcoding to demonstrate that many herbal supplements on the market aren’t what they’re supposed to be. According to these investigators, about one-third of all herbal products purchased by North American consumers contain no trace of the botanical ingredients listed on their labels, and many other products are adulterated with ingredients – wheat, soy, rice and other inexpensive fillers – that aren’t listed on the label. Even more disturbing was the revelation that some products contain unlisted ingredients, such as black walnut, that could trigger serious or even fatal reactions in people with allergies.

Justifiably, this study triggered concern among dietary supplement industry watchdogs. In February 2015, following an investigation in his state, New York Attorney General Eric Schneiderman directed several “big-box” marketers of herbal supplements to remove a number of products from their shelves and provide detailed information about testing, processing, production and quality control for the remainder of the herbal supplements they sell.

Such actions should serve as a precaution to supplement manufacturers, too many of whom cut corners (omitting routine laboratory analyses, for example) or, worse, knowingly market substandard or substituted products. DNA barcoding and other technologies are becoming more readily available and affordable, and they will make life increasingly difficult for careless or unscrupulous companies.

However, regardless of how sexy DNA barcoding may be, it’s important to remember that the technique has its limitations:

  • Much like the checkout scanners at the supermarket, DNA barcoding is used to “read” a short segment of genetic material from an unidentified organism. That scan is then compared to a database of known organisms. If the genetic material from the scanned organism has been altered during processing – say, by heat or chemical treatment – it might not be recognizable with DNA barcoding. Have you ever been delayed at the checkout counter when the scanner didn’t recognize the barcode on an item you were purchasing? The same thing can happen with DNA barcoding.
  • DNA barcoding is only useful if an organism’s genetic information is already in the database. Although the International Barcode of Life Project (the database used by the Canadian scientists) contains information for an impressive array of plants, it is by no means complete.
  • DNA barcoding is often ineffective for identifying highly purified or concentrated plant extracts, which may contain too little genetic material to be detected by the technology.
  • DNA barcoding can detect the presence of a specific plant in a given supplement, but it cannot determine the relative amounts of different plant extracts within that product. Therefore, inadvertent cross-contamination, such as might occur when different plants are grown in adjacent fields or processed in the same factory, could raise unjustified suspicions of adulteration.

For all of these reasons, DNA barcoding has not yet been validated as an acceptable analytical method for determining the integrity of herbal supplements. In 2007, the U.S. Food and Drug Administration established regulations requiring that all domestic and foreign manufacturers of dietary supplements adhere to current good manufacturing practices (cGMPs). These regulations stipulate a number of acceptable procedures for ensuring the identity, purity, stability, composition, and strength of dietary supplements. Further, cGMPs delineate the steps supplement manufacturers must take to quarantine incoming raw materials so contaminated or adulterated ingredients do not enter production lines. Finally, cGMPs specify the types of record-keeping that are necessary for confirming the consistency of a given manufacturer’s products and documenting its ongoing compliance with FDA regulations.

Validated, cGMP-compliant analytical procedures include inductively coupled plasma spectrometry, high-pressure liquid chromatography, gas chromatography, mass spectrometry, near-infrared spectrophotometry, microbiological analysis, peroxide analysis, USP dissolution and others. At this time, DNA barcoding is not generally considered necessary or even particularly useful for monitoring supplement quality or cGMP compliance. Besides, given the presence of so many substandard products on the shelves of some of America’s most trusted stores, it is doubtful adding DNA barcoding to the list of validated procedures would alter the behavior of manufacturers who are already non-compliant and intend to remain that way. These companies simply must be put out of business.

1.      Newmaster SG, Grguric M, Shanmughanandhan D, et al. BMC Medicine 2013, 11:222

2.      The New York Times. Anahad O'Connor. February 3, 2015