Herbal Medicines Adulterated, Contaminated or just plain Missing. It’s an International Scandal
Senior lecturer in Pharmacology at University of Adelaide
In the wake of the ABC statin story there have been a lot of comments on the Conversation about the evils of Big Pharma. Less attention has been given to Big Supplement, the multimillion dollar herbal supplement industry. Despite the known lack of efficacy of many herbal medicines, and the potential for harm, or contamination, the herbal medicine industry seems to get a free pass.
In the latest revelations, it appears that many herbal medicines have little, if any, of the ingredients on their labels. And what is there instead may be toxic.
The scope of the problem
Regulating herbal medicines can be quite difficult, if you want to ensure a herbal medicine has the mixture of herbs that the label states. In many cases the active ingredients are not known, so you cannot measure the active ingredients to make sure you are getting what you paid for. And most herbal medicines are presented as highly processed powders or teas. One pile of slightly greenish dust looks like another.
Worse still, even if you had access to the original plant, for many plants it takes an expert to tell them from other species that have no medicinal value, or one that may be even toxic.
Currently we largely rely on herbal companies to be honest about what goes into their products. But independent verification of the identity that what people are ingesting for their health is in fact the real deal is highly desirable. So how do you tell if the pile of finely ground plant material is the herb (or herbs) in question. Enter DNA Barcoding.
DNA Barcoding to identfy herbs in Herbal Medicine
DNA Barcoding is an approach to identifying species by looking at particular variable regions in a species DNA. All species are evolutionarily related, so the DNA of species that are very closely related is more similar to each other than species that are more distantly related. So in theory by sequencing the genes of enough species, we can identify which species otherwise unidentifiable tissue belongs to by comparing DNA from the said tissue to a bank of DNA from known species.
The principle is similar to that used in paternity testing and identifying disaster victims.
Simple in theory, complicated in practice, if you choose DNA sequences that don’t vary much, like housekeeping genes, then you can’t tell closely related species apart. If you chose highly variable genes, like the chunks of broken viruses that litter our genome, then more distant relatives will be lost in the noise.
For this research report, Canadian researchers created a DNA sequence bank from known herbs used in herbal medicine. They used sequences from two separate gene regions to improve selectivity and reduce false positives and false negatives. After doing blind testing of known herbal samples to ensure that the tests were selective and sensitive (i.e. when the test said herb x was present it really was present), they then examined 44 herbal products on sale in North America, sourced from Canada and the US.
What’s on the label is not what’s in the bottle
What did they find? Well, the primary finding was that nearly one in ten herbal medicines had no herbs in them, just filler.
I’ll repeat that. Nearly one in ten herbal medicines had no herbs in them. This is an astonishing result. Imagine the outrage if pharmaceutical companies were selling drugs with no active ingredient in them.
The rest of the news was no better, around a third of the herbal medicines had substitutions, where a different species was used instead of the one listed on the bottle. Around a third also had contaminants or fillers that were not listed on the labels.
Overall, less than half of the herbal medicines actually had what was listed on the label.
Seriously, they replaced an anti-depressive with a laxative. I just spent a good part of Saturday boiling up Senna pods (a story for another day), and I cannot even conceive of how you could get the two confused, even when chopped up. If the substitution was accidental, this is a fundamental failure of quality control and governance. If deliberate, words fail me.
Not only will Senna not relieve depression but Senna can have serious side effects including liver damage if used for some time (as you would with anti-depressants). And this was not the only case where a potentially toxic herb was substituted.
In other cases the contaminants were a serious worry. Many herbs were contaminated with Walnut, possibly leaves that got caught up in harvesting the authentic plant. These have the toxic chemical juglone in them.
Even the relatively harmless fillers can be an issue if they do not appear on the label. Wheat as a filler can be an issue to someone with gluten allergy.
This is not the first study to show contamination and substitution in herbal medicines, but it is the largest and most comprehensive in a developed country.
Australia is not immune
You might wish to take some comfort in the knowledge that Australia’s Therpaeutic Goods Administration treats herbal medicines as medicines. Unlike the United States, where they are treated as food supplements and monitored with less stringent rules than ours. But herbs for the Canadian study sourced in Canada, which has approaches to herbal medicines not dissimilar to ours, were found to have substantial contamination and substitution issues.
And the TGA’s rules will not necessarily help. The TGA relies on honesty from sponsors of herbal medicines when they are registered, with post marketing follow-up. This follow-up consists of random surveys and targeted surveys from concerns raised by consumers.
Given that there are over 10,000 licensed herbal medicines in Australia, and nearly 2000 new herbal medicines being registered each year, the number that can be checked by this method is rather small. In a TGA survey in 2009-2010, 110 complementary medicines were tested. An astonishing 90% of complimentary medicines surveyed were non-compliant with their licence conditions.
The license conditions cover everything from advertising and unsupported therapeutic claims to composition. Forty one (37%) of these non-compliance’s resulted in the sponsor withdrawing the medicine or the TGA revoking the licence. In the same time frame no prescription or over the counter medicine had their licences revoked.
We don’t exactly know what proportion of these revoked licences are due to herbal medicines having the wrong ingredients or being contaminated, but recent cancellation notices suggest that 11% of all cancellations are due to problems with component concentrations or contents. This sampling result indicates that Australia, like the rest of the developed world, has a significant problem.
The Herbal Medicine Industry is an international industry, with products travelling all over the world. The widespread substitution and contamination of herbal medicines is an international scandal. Despite the vigilance of the TGA, Australia is almost certainly not immune from this scandal.
Disclaimer: I’m one of a group of researchers who have just won an NHMRC grant to determine the extent of contamination and substitution of herbal medicines in Australia.