Some Herbal Products May Not be All They Seem

Many herbal products found to contain ingredients not listed on the label that could be potentially harmful to health

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Many people use herbal products as alternatives or supplements to medication. But are they really taking what they think they're taking?

A recent study found that many herbal products contained ingredients not listed on the label.

The researchers also found that some of the contaminants found are associated with serious health risks.

The researchers concluded that the overall low quality of herbal products could make the products less effective and therefore less valued by potential consumers of herbal products. The researchers suggested that the herbal product industry should adopt a testing standard.

"Tell your doctor about all supplements you use."

The lead author of this study was Steven G. Newmaster, PhD, BSc, from the Biodiversity Institute of Ontario at the University of Guelph in Guelph, Ontario.

The researchers tested 44 herbal products from 12 different companies. The products represented 30 different herb species.

In addition, the researchers tested 50 different leaf samples that contained 42 different plant species that included all the plants that were listed on the labels of the herbal products, as well as some closely related plant species.

They used DNA barcoding to test the purity of the herbal products. The products were single-ingredient, so if any additional barcodes were detected in each sample, it meant that the product was contaminated.

DNA barcoding allows researchers to identify specific species of a plant by using certain genetic markers. The researchers used an SRM (standard reference material) herbal barcode library in order to identify the unknown herbal products and leaf samples.

The researchers considered a product to be "authentic" if it contained a DNA barcode for the main ingredient listed on the label of a tested product. A product was considered "contaminated" if a barcode for a different species not listed on the label was found in addition to the authentic barcode.

A substitution occurred when the researchers found a barcode of a species that was not listed on the label and there was no authentic barcode found for the ingredient listed on the label.

A product contained "fillers" if the researchers found a barcode for ingredients that were common fillers, such as rice, soybean and wheat. These fillers could act either as ingredient substitutes or contaminants depending whether or not the barcode for the main listed ingredient was also present.

The researchers found that 48 percent of the tested products were authentic, but 59 percent of them were found to have plant species not listed on the label. The findings also showed that 33 percent of the authenticated products had contaminants or fillers that were not listed on the label.

The researchers determined that 75 percent of the 12 different companies had products that contained authentic ingredients. Only two out of the 12 companies were found to have products that did not have substitutions, contaminants or fillers in them.

In addition, the researchers were not able to authenticate any of the products that came from the other 25 percent of the companies represented.

Substitutions were found in 32 percent of the samples and in products from 83 percent of the companies. Fillers were detected in 21 percent of the products tested and in products from one-third of the companies.

The findings revealed that in many of the products, there were contaminants that are known to be toxic and have negative side effects and negative interactions with other herbal products or medications.

The researchers suggested that it was possible there were more unidentified contaminants in the products because the presence of, and information on, certain contaminants may not be known yet.

Many of the fillers that were found may be potential health risks to people who are allergic to that filler; for example, people with a gluten allergy could accidentally and unknowingly eat wheat because it was unlisted in a product. 

The researchers believe that the lack of authentication in herbal products is due to a lack of health standards for the manufacturing of these products. They suggested that the herbal product industry should adopt DNA barcoding as a standard for authenticating herbal products by testing the raw materials used in the products.

They argued that more authentic herbal products would make for safe, healthy alternatives to medication that can be trusted by consumers, which would support the business aspect of the herbal industry by not having the value of the products drop because consumers don't trust a product.

This study was published on October 11 in BMC Medicine.

The International Science and Technology Partnership Canada, the Humanities Research Council of Canada, the Ontario Genomics Institute, and the Canadian Foundation for Innovation provided funding.

Review Date: 
October 11, 2013
Last Updated:
October 14, 2013