Subpar supplements: Research reveals substantial adulteration in popular botanicals

12 Sep 2024 --- The Botanical Adulterants Prevention Program (BAPP) from the American Botanical Council (ABC) reveals adulteration rates of between 16.5% and 56.7% for five botanicals in a new review of 78 publications and 2,995 samples. The authors caution that reliable data on adulteration in botanical supplements and herbal medicine is lacking.

Adulteration was highest in ginkgo leaf extract samples (56.7%), followed by powdered plant materials or extracts of black cohosh root or rhizome (42.2%), echinacea root or herb (28.5%), elderberry (17.1%) and turmeric rhizome (16.5%). The study includes the most samples for turmeric (1,247), elderberry (695) and ginkgo leaf extract (533). 

Although these rates may not be representative of the overall adulteration rate in the industry, the authors stress that it is clear that “adulteration of botanical ingredients is a problem.”

“While there are many responsible manufacturers of high-quality botanical dietary supplements, the evidence from the paper suggests that adulteration unfortunately impacts a substantial part of the industry,” the study’s co-author Stefan Gafner, Ph.D., ABC’s chief science officer, tells Nutrition Insight. 

“It also shows that exact numbers of the extent of adulteration are unavailable and that any estimate we provide is based on data with several shortcomings. This also means that more robust information is needed on the quality of the herbal dietary and food supplement products on the market.” 

The study lists several challenges and limitations in determining an accurate number of adulterated products in a specific market. Results from a comprehensive analysis of all products sold may not be available, the criteria for what constitutes adulteration vary among researchers and some laboratory analytic methods to detect it may not be fit for this purpose. 

Identifying rates

Gafner highlights that questions from colleagues, industry members, health professionals and journalists on the extent of adulteration and whether it has become worse helped to initiate the research. 

“Since there were no reliable numbers on the frequency of adulteration that we could draw upon, we initiated our investigation using the available information from the published literature.”

Gafner explains that raw material costs, climate conditions and competition rates influence adulteration rates.He details that many factors impact the extent of adulteration: “More costly ingredients often have a higher risk of adulteration since there is more profit to be made for those who adulterate them.” 

“Climatic conditions can impact the adulteration rate. For example, a bad harvest can increase the adulteration rate for botanicals grown in a limited geographical area. This has been seen, for example, for saw palmetto extracts.” 

Moreover, Gafner explains that botanicals for which the market is very competitive also have a higher risk as procurement departments may push suppliers to lower their prices. “Sometimes, the supplier can only comply with the customer’s price demand by adding or substituting an ingredient of lower value to the labeled botanical,” he says. 

“This is one of the reasons why adulteration is fairly common in ginkgo leaf extract products. For elderberry, the sudden increase in the demand for such dietary supplements during the COVID-19 pandemic led to supply shortages, substantial price increases and increased frequency of adulteration.” 

Supplements versus herbal medicine

The researchers found that “not a single product” sold as a licensed or registered herbal medicine was adulterated, contrary to supplements. Gafner links this in part to how these markets are structured. 

He highlights that the dietary or food supplement market is very fragmented: “Hence, many companies compete for shelf space and market share, generally leading to a different price structure than what is seen in the herbal medicine market, where the registered or licensed products are regulated as medicines.” 

US FDA-issued warning letters to dietary supplement companies indicate that compliance with appropriate setting of specifications and adequate testing against these specifications is not always the case within the dietary supplement industry, says Gafner.

“Hence, a dietary supplement company may not detect adulterated materials in its quality control department.”

We discussed botanical adulteration in the industry with ABC at Natural Products Expo West this year.“Companies manufacturing registered or licensed herbal medicines often have a long history of producing such products, and the companies have been built around a focus on quality, although there are many dietary supplement manufacturers for which this is true as well.” 

Gafner explains that registered or licensed herbal medicines require the submission of a substantial amount of information about the product’s efficacy, safety and quality. 

“There are additional costs involved for regulatory compliance for the manufacturer — this includes appropriate laboratory test methods to ensure the quality of the products. These additional costs are built into the price structure of herbal medicines, which are generally sold at a much higher price than food supplements in Europe,” he adds.

Additional research needed

For the study published in Natural Products Reports, the researchers focused on five species with the most publicly available data, explains Gafner. In addition, the team focused on publications from 2000 or later “to make it more relevant to the current situation.”

The authors note that the identified adulteration rates align with previous studies using chemical and genetic identification methods. 

At the same time, they stress there were “notable constraints” in establishing an accurate estimate of adulteration in the global botanical supply chain. Therefore, they note that more research is needed to identify adulteration and develop specifications to discern when a product is adulterated and what constitutes an acceptable level of unlabeled excipients in raw materials.

More research is needed to identify adulteration and develop specifications to determine what constitutes adulteration.“In the ideal scenario, an investigation would analyze each dietary supplement product available in a given market using fit-for-purpose analytical test methods (since presumably more than one method would need to be used),” details Gafner. 

“We are not aware of any such large-scale investigations except unpublished data from the ABC regarding its testing of circa 500 commercial ginseng products sold in North America in the late 1990s (where about 25% were deemed adulterated or mislabeled).” 

Gafner notes that this scenario would eliminate discrepancies in the methods used and differences in a researcher’s or author’s assessment of what constitutes adulteration for a specific ingredient. “Such investigations would need to be repeated at a regular interval to determine any changes in adulteration frequency and to account for any new schemes,” he explains.

Additionally, Gafner suggests testing a smaller number of samples if it is possible to obtain a representative set of commercial botanical products from a specific market: “In this case, the results could be extrapolated to the entire market by appropriate statistics, similar to what is done during an election when a winner is predicted based on polling long before all the votes are counted.”

By Jolanda van Hal