Identity Testing for Dietary Supplements

The mass confusion around identity testing has brought more awareness to the issue, but the industry is still lacking clear guidance on how to deal with some of the practical issues.

How to Properly Conduct Identity Testing for Dietary Supplements

Verifying identity is like a lot of sciences drawn from multiple disciplines: it’s not usually plug-n-chug, and it requires replication of results to achieve meaningful conclusions. Luckily for science, there are valid ways to determine ID. They just take some thought, and in many cases, more than one test.

The thought behind ID requires some understanding of the context of the material being identified. Species expected, plant part, physical form, likelihood and type of adulterants, degree of processing and concentration all dictate what type of method should be used.

Believe it or not, identity testing is easy for a lot of botanical raw materials. Whole or cut herbs, fruits and roots are often easily distinguished by their quality, and by physical features such as size, shape, color and odor. However, we lose this ability when we take a whole leaf, dry it and grind it into a powder whose parts cannot be identified by microscope. At this point, we have to switch to chemical testing to determine what ancient terminology should be used, using classifications created hundreds of years ago by people for plants.

Luckily, whatever form of ID methods we choose, we still need to compare to a ‘reference’ or a sample of the plant as it exists in nature. So it’s really important to be sure the reference material is authentic and representative of the target species in the population, because it forms the entire basis for the test. The method itself should be based on clear and objective pass-fail criteria that includes at least one positive match to the species expected, plus in many cases for higher risk materials, at least one negative match to rule out a possible adulterant.

The documentation is as important as the activity. If it’s not in writing then it didn’t happen, says the auditor. One shortcut often taken for verifying ID is to write ‘conforms’ on the COA. But what, exactly, does the sample conform with? A memory of what the sample looks and smells like? A powder that has been verified to contain some of the same chemical markers as the expected species, which you are ‘pretty sure’ is 100% of the expected species? Or to a specific authenticated reference material? Because shortcuts on the reference are so often taken, it is best to list the reference material number used in the Certificate of Analysis for the sample, under ID Method. Accompanying the COA and available on request should be a test report which lists all methods, reference materials and their validations and verifications.

How to know your reference material is authentic? The best is to acquire whole fertile plant parts from a source that has authenticated the identity of the sample using a trained botanist or herbalist. For chemical testing, a lower grade of botanical references (milled powder, extract or liquid forms) are often used, but their validity as reference material are considered inferior or secondary in the absence of authentication and chain of custody to the whole plant part.

The difference between trusting the source of reference materials versus verifying it can make all the difference. For example, a bottle of olive oil purchased from the grocery store may be used as a reference standard without verifying the identity with testing. However, olive oil is known to be adulterated with other oils, so our trust in the label should not be sufficient to verify its identity. We need more proof, in the form of independent test reports using valid methods, that the olive oil is 100% from olives and is not adulterated, before we can consider it a valid reference material.

Botanical references, even authentic ones, are not ‘ready-made’ to reference all types of samples from the same species and plant part. Again, this is an area that requires some thought by laboratory technicians. For example, when a botanical is extracted or heated, chemical changes occur. To prevent the processing method from falsely impacting the match, a reference must undergo the same process as the sample, or else the chemical differences from heating falsely appear as differences between the species. So, if your sample was extracted in hot 70% ethanol for five hours, then the lab should prepare the reference in the same way.

Now, for the top 5 ID testing lessons they don’t teach in school:

1. Much of ID testing relies on a sufficient understanding of the material being tested. Communicate to the lab as much info as possible, such as specification and manufacturing process, so that they can make sure to prepare the reference standards correctly and select the correct method.
2. No ID method covers all potential adulterations or mis-identifications. And ID covers contamination if it may be considered harmful. Make sure you know what the risks are for your materials. Risk assessment for adulteration is necessarily a team effort across the supply chain, not something that ‘someone else should be doing’.
3. Authentic references and their preparation are as important (or more) than the method used. Always check the sources and make sure they are authenticated and representative of the species and identity.
4. Testing the same sample with different methods substantially improves the meaningfulness of any one test. High risk materials with known adulterants often need a test for a positive match to the species and a separate test for a negative match to the adulterant.
5. Many adulterants, especially newly developed ones, are not caught with typical ID methods, which is why strong specifications, and supplier verification is so important.

The issue of ID is not going away, and it’s a big issue in food now too (see sawdust in cheese, sushi that’s not sushi, etc). The wave of attention on food and supplement ID issues has not yet begun to crest, but now at least we know how to swim.

This article was originally published by Natural Products Insider in August 2016.