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Herbal supplements often contain substitutes, fillers and contaminants, study finds

A significant number of such products may contain none of the particular plant that’s supposed to be the product’s main ingredient.

herbal pills
CC/Flickr/Heather Bauer
Dietary supplements, including herbal ones, are generally considered safe until proven otherwise.

A majority of herbal products sold as alternative medicines in Canada and the United States may be contaminated with products not listed on their labels.

And a significant number of such products may contain none of the particular plant that’s supposed to be the product’s main ingredient.

That’s the troubling finding from a study published recently in the journal BMC Medicine.

Troubling, but not surprising. For this new study adds weight to longstanding concerns among health professionals that the herbal-supplement industry is rife with dubious practices, including out-and-out fraud, and that the ingredients in many of the supplements are not only ineffective, but sometimes dangerous.

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The World Health Organization has called the adulteration of herbal products a threat to consumer safety.

In North America, more than 1,000 companies are currently selling 29,000-plus herbal substances to consumers, according to background information in the new study. Such products generate more than $60 billion in annual revenues in the United States alone.

Most U.S. consumers are unaware, however, that successful lobbying of Congress by the supplement industry has tied the Food and Drug Administration’s hands when it comes to regulating these products. Dietary supplements, including herbal ones, are, by law, considered safe until proven otherwise. That means FDA regulators can act against mislabeled or even unsafe supplements only after they are on the market.

Method and findings

For the current study, a team of researchers at the University of Guelph in Ontario, Canada, employed DNA barcoding — a technique that uses short sequences of DNA to identify species — to test the authenticity of 44 herbal products. The products, which represented 12 companies and 30 different species of herbs, were bought at mainstream outlets, including supermarkets, health food stores and pharmacies, in the greater Toronto area. Some were also purchased online from U.S. distributors.

The DNA testing revealed that “what is listed on the label of herbal products is not always what is found within the product,” conclude the study’s authors.

Most of the products “were of poor quality” and included “considerable product substitution, contaminated and use of fillers,” they add.

The study specifically found the following:

  • 59 percent of the products tested contained species of plants not listed on the labels (fillers and contaminants).
  • 33 percent of the products contained no trace of the product’s main labeled ingredient.

Only 2 of the 12 companies provided authentic products without any unlabeled substitutions,  fillers and contaminants.

A potential health risk

Although the study’s authors do not cite any companies or products by name, they do provide several examples of fraudulent and even potentiaaly dangerous ingredient substitutions and additions:

  • One product labeled as containing St. John’s wort (Hypericum perforatum), which is sometimes taken to treat depression, contained no traces of that plant. Instead, the product contained another plant called Senna alexandrina.

“This is a serious health risk,” write the study’s authors, “as senna is a Food and Drug Administration (FDA)-approved non-prescription herbal laxative, which is not for prolonged use as it can cause adverse effects such as chronic diarrhea, cathartic colon, liver damage, abdominal pain, epidermal breakdown and blistering.”

“Such contamination would be particularly dangerous for a consumer with nut allergies,” the study’s authors note.

“Although feverfew has been used to treat fever, migraine headaches and arthritis, it does have negative side effects such as swelling and numbness of the mouth, oral ulcers, nausea, vomiting, abdominal pain, diarrhea, and flatulence,” the study’s authors point out. Feverfew can also interact with various medications, including those used to treat heart disease, and should never be consumed by pregnant women, the authors add.

‘Unethical activities’

The herbal product industry “suffers from unethical activities by some of the manufacturers, which includes false advertising, product substitution, contamination and use of fillers,” the study’s authors conclude.

They recommend that government regulators in both the U.S. and Canada be given more resources and that DNA barcoding be used to authenticate products and prevent substitution and contamination.

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Those two things are unlikely to happen any time soon in the United States, however, given the dietary supplement industry’s current influence with Congress.

So, in the meantime, caveat emptor.

You can download and read the study at the BMC Medicine website.