The herbal supplement industry has experienced a notable surge in demand driven by growing interest in immune support and natural health interventions. According to estimates, U.S. consumers spent approximately $9.6 billion on herbal dietary supplements (HDS) in 2019, and this amount has continued to rise. However, this surge has also highlighted a persistent concern about adulteration in the manufacturing process. Understanding what to look out for with popular herbal supplements and the importance of quality assurance practices, such as Current Good Manufacturing Practices (cGMP), can help both practitioners and consumers make informed decisions.

Adulteration in Botanical Manufacturing

Adulteration in herbal supplement manufacturing refers to the compromise of a product’s quality, authenticity, or safety. This can occur unintentionally, but it can also be the result of economically motivated adulteration (EMA). Both intentional and unintentional adulteration may involve substituting the declared botanical with lower-cost or unrelated species, diluting it with inactive plant material or fillers such as starch or rice flour, or using incorrect plant parts, for example, employing the leaves of a plant instead of the roots. In more concerning cases, manufacturers may omit or mislabel the scientific (Latin) name or plant part on the label or synthetically alter the product by adding pharmaceutical compounds to boost its perceived effectiveness.

Certain red flags on labels may help identify adulterated products. These include the absence of a Latin binomial (e.g., “turmeric” instead of Curcuma longa), failure to specify the plant part used (such as stating “gingko” without indicating “leaf”), and overly vague terminology like “proprietary blend” that lacks ingredient transparency. Additionally, the presence of undeclared excipients or artificial colorants may further indicate poor manufacturing integrity or attempts to mislead consumers about the product’s origin or quality. 

The Role of cGMP in Maintaining Quality and Safety

Current Good Manufacturing Practices (cGMP), established by the U.S. Food and Drug Administration (FDA) under 21 CFR Part 111, are a critical framework for ensuring the quality, safety, and traceability of dietary supplements, including botanical formulations. These standards require manufacturers to confirm the identity of each botanical ingredient using validated techniques such as microscopy, high-performance liquid chromatography (HPLC), or DNA barcoding. 

While the FDA regulates cGMP regulations very carefully, there is still confusion surrounding the concept of “botanical integrity” for dietary supplements, despite “quality” and “integrity” being regulated terms. 

With this in mind, it is essential that practitioners and consumers alike understand the concepts of purity, potency, ingredient transparency on labels, and trustworthy ingredient origins. Purity requires rigorous testing to rule out contamination by heavy metals, pesticides, or microbial pathogens. The potency of active constituents, such as curcuminoids in turmeric, should be provided across all product batches for maximal transparency. Additionally, product labels should accurately reflect the ingredients and their proportions, while also being forthcoming about their origins and the handling process from harvest to the final product.

Compliance with cGMP is particularly critical in a burgeoning market, where diminished regulatory oversight may provide increased opportunities for contaminated materials to infiltrate the marketplace. Manufacturers who are dedicated to cGMP standards are strategically better equipped to protect their products from these threats while maintaining the trust of both practitioners and consumers.

Common Contaminants and Quality Issues in Botanical Supplements

In addition to the issue of botanical adulteration, numerous other quality threats can compromise the safety, efficacy, and reliability of herbal supplements. One significant concern is dilution, in which the incorporation of inert fillers, such as rice flour or other starches, intentionally weakens the active botanical material. Not only does this mislead consumers about the product's potency, but it also undermines the clinical outcomes for practitioners who use supplement interventions in their personalized protocols for clients. 

Potency variability represents another significant concern. Botanical products may exhibit considerable fluctuations in the levels of active constituents, such as curcuminoids in turmeric or anthocyanins in elderberry, across different batches, which can ultimately lead to inconsistent efficacy.

Environmental and processing-related contaminants present significant concerns. Heavy metals (e.g., lead, arsenic, mercury, cadmium) may accumulate in botanicals as a consequence of contaminated soil or irrigation water, thereby posing neurotoxic, nephrotoxic, and carcinogenic risks. Additionally, pesticide residues originating from agricultural inputs are frequently observed, particularly in botanicals sourced from nations with less stringent regulatory oversight. Residual solvents used during extraction processes may persist in the final product if not adequately evaporated or removed; these solvents can include hazardous compounds such as ethanol or methanol if not managed properly.

Moreover, microbial contamination has emerged as a recurring concern in botanicals that are either inadequately manufactured or improperly stored. This issue encompasses yeast and mold, which not only undermine shelf life but can also generate mycotoxins, such as aflatoxins, that possess carcinogenic properties. The presence of fungi, regardless of visibility, raises substantial concerns regarding immune safety, liver health, and gastrointestinal irritation, particularly for individuals who are immunocompromised.

These issues underscore the critical importance of comprehensive quality testing at every stage of the production process. Reputable manufacturers utilize validated analytical techniques, including HPLC, gas chromatography, microbial plating, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for the detection and quantification of contaminants. Furthermore, implementing appropriate storage conditions and handling practices is essential to prevent microbial growth and preserve the integrity of bioactive compounds.

5 Popular Herbs: Background and Adulteration Risks

Black cohosh, echinacea, elderberry, ginkgo, and turmeric are among the most widely used herbs in clinical and consumer health settings, yet they face ongoing challenges related to adulterated manufacturing that threaten both safety and efficacy. These botanicals are often targeted due to high global demand, complex supply chains, and the variability of active constituents across species and plant parts. Adulteration may occur through species substitution, dilution, synthetic enhancement, or mislabeling, compromising product quality and misleading both practitioners and consumers. Understanding the unique vulnerabilities of these high-profile herbs is crucial for making informed choices and ensuring reliable product outcomes.

Black Cohosh (Actaea racemosa)

Black Cohosh (Actaea racemosa, previously known as Cimicifuga racemosa) is often used to support hormonal balance, especially in women with menopause-related discomfort. Its main active compounds are triterpene glycosides and phenolic acids. Common adulteration involves substituting it with Asian species, such as Actaea foetida or A. cimicifuga, which can be toxic to the liver. Some products also contain aerial plant parts instead of roots or use outdated taxonomy in labeling. 

In a systematic review of 21 global studies published between 2000 and 2023, 42% of the 320 black cohosh samples were found to be adulterated. Notably, of the 166 samples from North America (the United States and Canada), 32% were determined to be adulterated, highlighting the importance of quality control in botanical manufacturing. To ensure optimal quality, look for products labeled as Actaea racemosa (root) that have been verified through DNA testing or high-performance thin-layer chromatography (HPTLC). 

Echinacea (Echinacea angustifolia)

Echinacea species, particularly Echinacea purpurea and Echinacea angustifolia, are widely recognized for their immune-modulating properties and support in common colds and flu. These species contain caffeic acid derivatives, polysaccharides, and alkylamides. Alkylamides from the plant can help identify the species through their phenolic constituents, making partial or entire substitutions easier to spot. Adulteration may occur through substitution with unrelated plants, such as Parthenium integrifolium (Asteraceae), Lespedeza capitata (Fabaceae), Eryngium aquaticum (Apiaceae), Rudbeckia nitida (Asteraceae), Helianthus annuus (Asteraceae), Liatris aspera (Asteraceae), and Cistanche species (Orobanchaceae), or by using only aerial parts, even though the roots are preferred for their potency. Proper labeling should clearly identify the specific species used and indicate whether the extract comes from aerial parts or the roots.

Elderberry (Sambucus nigra)

Elderberry (Sambucus nigra), renowned for its immune-supporting properties and efficacy in aiding recovery from common colds or flu, possesses a high concentration of anthocyanins and flavonoids. It is frequently adulterated with other species of Sambucus, such as S. canadensis or S. ebulus, which exhibit variations in chemical composition. In certain instances, manufacturers may dilute elderberry extracts with alternative anthocyanin-rich fruits, including black rice or black currant, or incorporate undeclared sweeteners in syrup formulations. To ensure the quality of the product, it is advisable to seek items that are explicitly labeled as Sambucus nigra (berry or fruit), and consider specification detailing the standardization of anthocyanin content. Ideally, these products should be processed without the utilization of solvents or genetically modified organisms (GMOs).

Ginkgo (Ginkgo biloba)

Ginkgo (Ginkgo biloba), commonly utilized for cognitive support and circulatory health, contains bioactive compounds including flavanol glycosides and terpene lactones (e.g., ginkgolides). It is often subject to adulteration through dilution with flavonoid-rich but unrelated plants, such as Sophora japonica, the incorporation of synthetic flavonoids, or the utilization of non-leaf plant parts, including stems or twigs. 

In a systematic review of 28 global studies published between 2000 and 2023, the authenticity of ginkgo products was evaluated, revealing that 57% of the samples were found to be adulterated. To ensure product authenticity, labels must explicitly indicate the presence of Ginkgo biloba (leaf), with standardized content for flavonol glycosides and terpene lactones.

Turmeric (Curcuma longa)

Turmeric (Curcuma longa) is widely recognized for its antioxidant properties, as it is abundant in curcuminoids and volatile oils. Nonetheless, it is frequently adulterated with synthetic curcumin or colored with hazardous substances such as lead chromate, either from the soil or to augment its visual appeal. Certain manufacturers may substitute it with alternative Curcuma species, such as Curcuma zedoaria, which may exhibit variations in both efficacy and safety. Labels should accurately indicate Curcuma longa (rhizome), with standardized content for curcuminoids, and should provide traceable sourcing.

Overall, it is evident that the demand for botanical supplements continues to grow, as does the importance of ensuring their quality, safety, and authenticity. The risks associated with adulteration in botanical supplement manufacturing, whether through species substitution, contamination, or mislabeling, can significantly compromise both clinical efficacy and consumer safety. When these issues are further compounded by the presence of residual solvents, heavy metals, microbial contamination, and inconsistent potency, the necessity for rigorous oversight becomes evident. By recognizing these signs, verifying the accurate identification of plant species and their parts, and selecting products manufactured in accordance with cGMP standards, practitioners and consumers can make more informed decisions. This proactive approach not only supports improved health outcomes but also promotes the credibility and effectiveness of botanical medicine in clinical practice.

To learn more about botanicals and their role in overall health:  

Clarifying the Role of Elderberry for Immune Support

Curcumin and Cognitive Function

Herbal Echinacea for Upper Respiratory Tract Health

Resveratrol and Curcumin to Promote Mitochondrial Biogenesis

By Rachel B. Johnson, MS, CNS, LDN