Skip Lot Testing Misses the Mark

For true quality control, supplement manufacturers need to test every batch of raw materials

By Beth Baldwin-lien, ND

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The very first article in the Natural Medicine Journal Quality Standards series was titled “Beyond Testing: Ensuring Supplement Quality.” And so it seems appropriate to take a step back for a moment and discuss the importance of quality assurance testing before moving beyond it.
As noted in previous articles, any ingredient in a dietary supplement may be sourced from multiple suppliers around the globe. The variously sourced materials then may be mixed together and sold to the supplement manufacturer by a vendor as a single ingredient.
It is the supplement manufacturer’s responsibility to ensure that each product contains what it claims and is not contaminated with other substances. However, the guidelines for doing so set forth by industry-developed qualification programs typically only require testing of material identity, potency, and microbiology contamination. Federal regulatory requirements call for the same, with the addition of stability testing—storing a sample of finished product to be retested for identity, potency, and microbiology at intervals to ensure product stability through the expiration date.
For all other information about potential contaminants in a supplement, the manufacturer is currently allowed to rely on a certificate of analysis from the raw material vendor. The supplement manufacturer does bear the responsibility for verifying the authenticity of the certificate of analysis, but vendors may be “qualified” using a vendor qualification process, after which the manufacturer may perform skip lot testing to periodically confirm this “qualification.”
So unless vertically integrated from seed to finished product, each manufacturer of dietary supplements must ultimately choose whether to test every receipt of raw material for identity, potency, and any known possible contaminants, or to qualify their raw material suppliers to be reliable vendors of acceptable-quality materials, and perform skip-lot testing verification. The majority of dietary supplement manufacturers fall into the latter category.

The Allure and Downsides of Skip Lot Testing

Most supplement manufacturers do skip lot testing because it is far cheaper, requiring less labor and less paperwork. Furthermore, there is a widespread belief and trust at every level of the industry that manufacturers that have established long-term relationships with reliable suppliers are less likely to encounter fraudulent or contaminated material.
Yet any company that actually tests every receipt of raw material at its manufacturing facility—of which there are very few—can attest that certificates of analysis are often inaccurate, whether through fraudulence or honest error. It may be less likely or less common to receive contaminated material from a familiar wholesaler with an excellent reputation, but it certainly is not impossible.
Most supplement manufacturers do skip lot testing because it is far cheaper, requiring less labor and less paperwork.
Case in point: Recently Vital Nutrients, a supplement manufacturer that tests every receipt of raw material for all applicable quality parameters, discovered several pesticides, including DDT and DDT breakdown products, on a batch of valerian obtained from a raw materials supplier with a very strong reputation in the industry. The supplier had decades of experience extracting this product, and due to a strong correlation historically between undetectable pesticide levels on their own starting material and undetectable pesticide levels on their finished extract, their standard operating procedures required testing of their starting material only, not the finished product.
If Vital Nutrients were one of the majority of companies who perform skip lot testing, this incident would most likely have either gone undetected, passing DDT pesticide contamination on to the end user—the patient—or resulted in a product recall, generating a cascade of events for the practitioner, who is required by law to track and contact each purchaser of the recalled item. Thus dietary supplement recalls are potentially harmful not only to a patient’s health, but also to the reputation and business of every practitioner who sells nutraceuticals.
As stated in a previous article, “Dietary supplement recalls typically result from the discovery of an ‘out of specification’ finding in a product that has already been released into commerce,” prompted either by consumer complaints or post-release testing, with the most common reasons for recalls being “undeclared allergens, mislabeling, the presence of contaminants, questionable stability, and incorrect potency.” Obviously the likelihood of such a recall is drastically reduced when supplement manufacturers do their due diligence by testing every batch of raw material, so that any “out of specification findings” are tested for and discovered before, not after, releasing a product into commerce.
Regardless of the raw material supplier, and how well-qualified, trusted, and respected they may be, a product has typically had numerous opportunities for exposure to contamination by the time it reaches the consumer—(eg, growing in soil that contains heavy metals; potential exposure to herbicides, pesticides, or fungicides; plant material being extracted with solvent; packaging machinery that contains traces of industrial cleaners).
Using skip lot testing or relying on a vendor’s reputation or certificate of analysis is simply not an adequate to protect your patients, or to prevent product recalls that may negatively impact your practice.

About the Author

Beth Baldwin-Lien, ND, is a graduate of Bastyr University and has been a licensed naturopathic physician since 2004. In that time, she has worked in private practice, clinical research, natural product development, and as the medicinary manager for the community clinics program at the National College of Natural Medicine. Baldwin-Lien resides in Portland and is a member of the Oregon Association of Naturopathic Physicians. She currently works in medical affairs and education for Vital Nutrients, a professional nutraceutical manufacturer headquartered in Middletown, Conn.