In 2019, researchers investigating why so many children in Bangladesh had high levels of lead in their blood traced a big part of the problem to something sitting in almost every kitchen: turmeric. Some processors had been dusting the roots with lead chromate, an industrial yellow pigment, to make dull batches look bright and premium. Nobody tasting a curry would ever have known.
That case is extreme, but the habit behind it isn't rare. Herbs get swapped for cheaper look-alikes, stretched with fillers, or "spiked" with chemicals that fool the very tests meant to catch them. And most of the time, the person buying the raw material has no idea. In this post we'll look at real, documented cases of herbal adulteration, what they tell us about where the system breaks down, and why testing against a botanical reference material is one of the most reliable ways to catch a fake before it reaches a product.
How Big Is the Problem, Really?
It's easy to assume adulteration is a fringe issue. The published numbers say otherwise.
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In 2013, a study in BMC Medicine used DNA barcoding on 44 herbal products from 12 companies. 59% contained DNA from plant species not listed on the label, and 21% contained undeclared fillers such as rice, soybean and wheat.
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A 2024 review in Natural Product Reports, part of the ABC-AHP-NCNPR Botanical Adulterants Prevention Program, pulled together published testing data. It found adulteration in 56.7% of ginkgo leaf samples, 42.2% of black cohosh, 28.5% of echinacea, 17.1% of elderberry and 16.5% of turmeric.
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The same authors stress that these figures depend heavily on how and where samples were collected. That's exactly why consistent testing methods matter so much. These aren't obscure herbs. They're some of the best-selling botanicals in the world.
Case 1: Turmeric and Lead Chromate
Turmeric is valued for its colour, and colour is also what makes it easy to cheat. A brighter yellow often sells for a higher price.
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Researchers from Stanford University linked elevated blood lead levels in Bangladesh to lead chromate added to turmeric during processing.
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After awareness campaigns and enforcement by Bangladeshi authorities, the share of market turmeric samples containing detectable lead dropped from 47% in 2019 to 0% by early 2021.
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A later multi-country survey covering India, Nepal, Pakistan and Sri Lanka found lead chromate in about 7% of samples and metanil yellow, a synthetic dye, in about 3%.
The lesson here is that a powder can look perfect and still fail badly on identity and safety. Ayurvedic supplement safety testing goes deeper into the heavy metals side of this.
Case 2: Ginkgo Extract "Spiked" to Pass the Test
Ginkgo is a good example of adulteration designed to beat the lab.
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Ginkgo extracts are usually standardised to a set level of flavonol glycosides.
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Some suppliers have been found adding cheap rutin or quercetin, often sourced from other plants such as Japanese sophora, to hit that number artificially.
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A simple total-flavonoid test can't tell the difference. The number looks right even though the extract isn't what it claims to be.
This is why identity testing has to look at the full chemical picture of a plant, not just one marker.
Case 3: Black Cohosh and Its Asian Relatives
Black cohosh (Actaea racemosa) is a North American plant used in women's health supplements. Its close relatives from Asia are cheaper and widely available.
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Several studies have found black cohosh products containing Asian Actaea species instead of, or mixed with, the real thing.
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These species look very similar once dried and powdered.
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Their chemistry is different, so the product may not behave the way the label promises.
Once a root is ground, your eyes are no help at all. Only a proper comparison can settle it.
Why Standard Checks Miss Adulteration
Most adulteration slips through because of gaps in how materials are checked, not because labs are careless.
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Visual and sensory checks fail with powders and extracts.
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Single-marker tests can be gamed by adding that one compound.
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DNA testing is useful for raw plant material but struggles with heavily processed extracts, where DNA breaks down.
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Supplier paperwork is only as good as the testing behind it. If you're not sure what to look for, our guide on what a COA actually tells you is a good place to start.
How a BRM Catches the Fake
This is where a botanical reference material earns its place. A BRM is a verified, authenticated sample of the genuine plant. It gives the lab something real to compare against, rather than a description in a book.
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Side-by-side fingerprinting: In HPTLC identity testing, the test sample and the BRM run on the same plate. The pattern of bands acts like a chemical fingerprint.
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Missing or extra bands stand out: A substitute species, a filler or a spiking compound changes the pattern in ways an analyst can see.
What Manufacturers Can Do Today
You don't need to overhaul your whole quality system to cut your risk.
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Test every new supplier's material for identity before approving it, not just after a problem appears.
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Keep a matching BRM on file for every botanical you buy regularly. You can see what's available in our BRM range.
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Don't rely on a single marker compound for high-risk herbs like ginkgo, turmeric and black cohosh.
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Make sure your QC team is trained to read HPTLC fingerprints with confidence. A good method is only as good as the person interpreting it.
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Re-test periodically, even with trusted suppliers, because sources and harvests change.
The Bottom Line
Every case above has the same pattern. The material looked right, the paperwork looked right, and the problem only showed up when someone compared it against the genuine plant. Adulteration works because it's hard to see. A botanical reference material makes it visible. For any manufacturer serious about quality, that comparison isn't optional. It's the starting point.
Sources:
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Newmaster SG et al. (2013). DNA barcoding detects contamination and substitution in North American herbal products. BMC Medicine, 11:222. https://bmcmedicine.biomedcentral.com/articles/10.1186/1741-7015-11-222
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Gafner S et al. (2024). Estimating the extent of adulteration of the popular herbs black cohosh, echinacea, elder berry, ginkgo, and turmeric. Natural Product Reports. https://pubs.rsc.org/en/content/articlelanding/2024/np/d4np00014e
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Forsyth JE et al. (2019). Turmeric means "yellow" in Bengali: Lead chromate pigments added to turmeric threaten public health across Bangladesh. Environmental Research. https://doi.org/10.1016/j.envres.2019.108722
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Review on botanical ingredient forensics (PMC). https://pmc.ncbi.nlm.nih.gov/articles/PMC9972475/
Frequently Asked Questions
What is herbal adulteration?
Which herbs are most commonly adulterated?
Can adulteration be detected by looking at the powder?
How does a BRM help detect adulteration?
Is DNA testing enough on its own?
How often should raw materials be tested for identity?
