Did you hear the outcry when a recent study reported that many herbal supplements aren’t what they claim to be? It reminded me of the big “fish switcheroo” scam from several years ago, when many markets and restaurants were found to be selling falsely labeled seafood…so customers were paying for red snapper, for instance, but wound up with perch.

Researchers from Canada used the same type of high-tech DNA analysis as was used to expose the seafood scam to make similar conclusions about herbal supplements. According to their study, more than half of the products they tested were contaminated with ingredients other than what was on the labels…and about one-third contained absolutely none of the material that was on the labels.

If valid, these findings are outrageous! But what if the researchers are wrong…?

The study has attracted a lot of attention from supplement naysayers, who point to it as evidence that dietary supplements are worthless…and from supplement-industry supporters, who say that the study had serious flaws. Daily Health News set out to find the truthand what we learned will no doubt surprise you…


Researchers from the University of Guelph in Ontario used a technique they created, called DNA barcoding, which identifies species. They sequenced two particular segments of the DNA from 44 herbal products from 12 different manufacturers that were supposed to represent 30 different species of herbs. All of these products are commercially available in the US and Canada.

By reading the DNA barcode, which is unique to each species, and then comparing it to an established library of DNA barcodes, the researchers were able to identify the plant material in their tested samples. Because they selected only single-herb products, they expected to find DNA from only one species of plant in each supplement.

The results, however, were not at all what they expected (numbers below do not add up to 100% because some categories overlap)…

• Just 32% of the herbal products tested contained the herb listed on the label and only that herb, nothing else.

• 59% of the products contained plant species that were not listed on the label.

• 32% of the samples contained absolutely none of the herb listed on the label, but instead contained some other plant species.

• 9% of the samples were complete junk specifically, three of the 44 products contained only rice and one contained only wheat.

• In some cases, the product contained an ingredient that is potentially harmful to everyone. For instance, one bottle labeled as St. John’s wort (typically used to combat depression) actually contained only Senna alexandrina, a completely different species of plant that is a very powerful laxative.

This study, which was certainly not the first published documentation of substitution in the herbal supplement industry, made the news in a big way—and made many people angry. Consumers wondered whether they had been throwing away their money…and some supplement manufacturers became defensive, calling the study findings invalid.

Among the critics of the new study is Stefan Gafner, PhD, chief scientific officer of the American Botanical Council (ABC), a trade group that promotes the use of herbal supplements. Dr. Gafner does not deny that adulteration in supplements is a problem. In fact, he is a member of a consortium focused on identifying and eliminating intentional and accidental adulteration of plant-based health products. However, he contends that this study has too many flaws to be credible.


When it’s done properly, DNA barcoding is a legitimate technology for accurately identifying plant materialbut in this study, Dr. Gafner said, the results may all be meaningless. I asked him to tell me why. His responses didn’t seem convincing enough to me to call the study into serious question. Nonetheless, I investigated his points and used some of them to challenge another scientist who has a big role in this fraySteven Newmaster, PhD, professor and botanical director at the Biodiversity Institute of Ontario and Centre for Biodiversity Genomics at the University of Guelph. He is the lead author of the study that Dr. Gafner calls meaningless.

Dr. Gafner’s criticisms of the herbal supplement study include concerns about the following…

• THE TESTING TECHNIQUE. DNA barcoding works on plant material in a fairly unprocessed form. “However, when leaves are exposed to heat, the DNA is often ‘denatured,’ yet the herb still retains its natural phytochemical properties. In other words, the DNA is modified in a way that makes it no longer useful to barcode, but the medicinal benefits of the herb aren’t affectedbecause the benefits of herbals are due to unique secondary metabolites rather than DNA,” Dr. Gafner said. “If herbs are extracted with alcohol (to pull certain chemicals out of the plant, as is done in preparing many dietary supplements), no DNA or only very fragmented DNA will be in the product. Since the method used by Dr. Newmaster can find minute amounts of DNA, the DNA that’s from botanical ‘fillers’ (other, different plants added by manufacturers) or from a previously analyzed plant that the research lab failed to clean off of its equipment can be easily picked up.”

Dr. Newmaster’s response: For 90% of the herbal species tested, at least one company’s product did yield the correct identity on the DNA test. That finding not only indicates the authenticity of that particular brand, he said, it also confirms that the manufacturing process does not destroy the DNAthus validating barcoding as a method of identifying the species. In fact, Dr. Newmaster said, there are more than 70 published papers that show you can get DNA from these products.

Contamination from unclean lab equipment, Dr. Newmaster continued, was not at all likely given his lab’s strict procedures. But even if it did occur, he said, it would have been highly unlikely to affect the study’s final results. “If we go to a product and pull some DNA that doesn’t match what’s on the label, we might suspect that it is due to contamination in the labif we did the test only once. But one thing we do in science is we reproduce. For every sample we had, we ran the test up to 20 times. We plotted what we got each time on a figure called a sample area curve. We kept sampling until the curve leveled off at one sequence, and then that sequence was matched to our DNA barcoding library, and that told us what the herb was. The evidence is dead strong.”

To provide more evidence that cross-contamination was not likely, the researchers also did a blind test on 50 control leaves from horticultural greenhousesand all of the DNA that was picked up during that testing provided direct matches with the plants requested from the greenhouses.

Furthermore, the University of Guelph, where this research was conducted, is home to the International Barcode of Life, the largest DNA barcoding laboratory in the world. The study used the same technology as was used to uncover the seafood industry’s false labeling a few years ago. In other words, this laboratory, which has barcoded about 2.8 million samples to date, is not a rookie or fly-by-night operation.

• ERRORS. The study researchers matched DNA extracted from several of the products they tested to the herb Parthenium hysterophorus, which they called “feverfew” in their report. None of these products were supposed to contain feverfew, and the study noted that feverfew’s potential side effects include swelling and numbness of the mouth, oral ulcers, gastrointestinal upset and increased risk for bleeding. Dr. Gafner’s concern is that feverfew is actually the common name for a different species, Tanacetum parthenium…and Parthenium hysterophorus is a distant cousin of feverfew that is more correctly called Santa Maria feverfew. He said, “Writing about the side effects of T. parthenium rather than P. hysterophorus is like saying that drinking too much coffee is not good for your health but then using clinical studies on drinking tea to support your argument.”

My review of the US Department of Agriculture’s plant database shows that Parthenium hysterophorus is commonly referred to as Santa Maria feverfew, while Tanacetum parthenium just goes by the name feverfew. But the National Institutes of Health and other peer-reviewed medical literature indicate that the names Santa Maria feverfew and feverfew are sometimes used interchangeably. I agree with Dr. Gafner that researchers should not report on products contaminated with one type of feverfew, then caution about the potential side effects of a different type of feverfew. However, this does not negate the fact that neither feverfew nor Santa Maria feverfew belonged in the products that were supposed to be either echinacea, a popular herb used to combat colds…or taraxacum (dandelion), used as a diuretic and detoxifier.

Study critics also point to spelling errors and inconsistent use of a scientific name of one of the tested products as a basis for being suspicious about the reliability of the study. Their point is that researchers who are careless and inconsistent with spelling and taxonomy might also be careless with lab protocol.

The study authors acknowledged that the paper does have a spelling error (“One misspelled word out of 9,184 wordsgive us a break!” Dr. Newcastle said) and other “administrative” errors, including one unintentional omission of a species name that led the critics to charge the authors with making speculations rather than scientific conclusions.

Our take on this: Spelling errors and inadvertent word substitutions are unprofessional and unfortunate…but they also are fairly common, even in peer-reviewed journal articles that are checked by many authors, editors and proofreaders prior to publication. At Daily Health News, we review hundreds of studies each year and can attest to the fact that scientific journals frequently contain not only mistakes in spelling, but also calculation errors and other more substantive errors that aren’t noticed by the studies’ authors until some careful reader points them out. In my opinion, such errors do not automatically invalidate all the findings in what are otherwise well-done studies.

• “FILLERS.” The Canadian researchers found that some of the herbal products contained cheap, common fillers, none of which were listed on the products’ labels. For instance, rice and soy were found in 21% of the products, alfalfa was found in 16% of the products and wheat was detected in one product. Failure to list these fillers on product labels could spell trouble for consumers with an intolerance or allergy to those ingredients.

Dr. Gafner contested the notion that fillers should be classified as “contaminants,” telling me that there are legitimate and appropriate uses for fillers and other ingredients in herbal supplements. For instance, he said, “Other ingredients frequently are added during the manufacturing process so the powder flows freely or so the product doesn’t absorb moisture from the air. Or a filler may be added to fill up a capsule so that consumers don’t see half-filled capsules and think they’ve been cheated.”

But have consumers been cheated? Well, yes, in the sense that the FDA requires all ingredients contained in the product to be listed. While Dr. Gafner does not consider the use of fillers unethical, he did agree that when fillers are used, they should be on a product’s label.


Critics of his study may not believe this, Dr. Newmaster said, but unless they want herbal products to be mislabeled, he is on their sidehe is not against herbal supplements. In fact, he believes that herbal supplements can be useful remedies. “As a plant medicine scientist, I believe in herbal products and I take them myself. What bothers me is that when there is substitution, it takes away from the efficacythe medicinal benefitof the herb,” he said. (He also reported that neither he nor his laboratory receives any funding from pharmaceutical companieswhich compete with herbal companiesnor from any private sector businesses.)

Dr. Newmaster said that he did not set out to vilify the herbal-supplement industry. “I believe that the supplement manufacturers also are victims of product contamination,” he told me. “I suspect that product substitution and contamination happens earlier in the supply chain, before the supplement manufacturers buy their bulk materialsand I suspect that the manufacturers don’t even know that this is happening.”

Dr. Gafner contested the idea that the supplement industry is clueless about what’s in its products, saying that several reputable organizations have published research on various microscopic, macroscopic and chemical methods for authenticating botanical raw materials. And he added that all supplement manufacturers and importers in the US are required to comply with the rules of the current “good manufacturing practices” in the federal Dietary Supplement Health and Education Act of 1994, which includes use of adequate testing. Still, he conceded that currently there is no single uniform method for authenticating herbal products.

Part of the problem is that although the Food and Drug Administration (FDA) is responsible for oversight of the supplement industry, it does not routinely test supplement ingredients nor frequently inspect manufacturing facilities. This means that supplement manufacturers are largely left to operate on the honor system. In my opinion, that system is no more appropriate for the supplement industry than it would be for the drug industry.


Of the 12 companies with products that were tested, only two provided authentic products with no fillers or substitutionsand the names of those two companies were not revealed by the researchers. In fact, the researchers did not provide the brand names of any of the products they tested…which brings us to my biggest criticism of the Canadian study. As a supplement consumer, I certainly want to know which brands passed muster and which did not! So why was this information omitted from the study?

Dr. Newmaster’s response to my question was, shall we say, oblique. “We provide an unbiased ‘watchdog’ service. The herbal industry has been alerted to a problem, and now it has the ability to take action,” he told me.

Without access to the desired information on specific brands, consumers are left to wonder how to buy supplements without worrying that we’re getting a bottle full of useless riceor worseinstead of the health aid we wanted. Right now, a colleague of Dr. Newmaster is using the exact same barcoding technology to help the FDA in an ongoing effort to spot fake fish products. It may be just a matter of time before DNA barcoding is used routinely on all products made from living materials, including herbal supplements, helping to make products safer and of higher quality. Until then, here are some tips for consumers…

• Do your research, suggested Dr. Gafner—but don’t rely on Google or other basic search engines, or you might be misled by the thousands of hits that aren’t associated with clinical trials. Better: Search PubMed, which is a search engine for medical literature…or Google Scholar, which provides a search of scholarly literature across many disciplines and sources. In the search bar, type in the brand and product name of any product you are considering using to help you find out whether a particular manufacturer has invested in clinical research.

• If an herbal product you currently are using is working for you, stick with it, suggested Dr. Newmaster. Otherwise, try a different brand. If a product makes you feel at all unwell, stop using it immediately!

• Order your supplements through a licensed naturopathic doctor rather than buying them over the counter. These physicians have access to professional-grade supplements that are likely to have undergone quality-assurance testing and/or that have been shown to be effective for the doctors’ other patients…so you can feel more confident that what you’re swallowing actually is what it claims to be. Or try the professional-grade brands that naturopathic physicians prescribe—Douglas Laboratories, Eclectic Institute, Priority One, Pure Encapsulations, Thorne Research and Wise Woman Herbals.