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What you see might not be what you get.
I often hear a criticism coming from the alternative medicine industry that pharmaceutical drugs are not tested properly because all possible interactions of all drugs at all concentrations are not done. This is a true statement, much like the statement that car safety can not be fully evaluated unless an example of every make and model is tested by crashing it into all possible examples of cars on Australian roads at all possible speeds. Just because something is impossible doesn't mean it can't be done, apparently.
Whenever I'm confronted with this claim I refer to the shelves of alternative potions in my local pharmacy, health food shop or supermarket, with particular attention to preparations which contain mixtures of ingredients, and ask if any of these interactions have ever been tested. The replies are inevitably either silence or non sequitur.
One difference between regulated pharmaceutical drugs and alternatives is how much you can rely on the labels. I can look at my packets of metformin, antihistamines or headache tablets and be reasonably confident that the pills contain the chemicals specified in the stated proportions. With the obvious exception of homeopathy (where no active ingredients are present) I can't be this confident about some of those bottles on the shelves I mentioned. This particularly applies to herbal preparations, simply due to the inherent variability of the chemical makeup of plant products. Making wine is probably the oldest example of transforming agricultural products, but even the best winemaker can't guarantee that wines made from grapes from the same vines will be exactly the same for each vintage. If I pick up a bottle of herbs it might say on the label what the active ingredient is supposed to be (but rarely does), but there is no guarantee that the concentration will be the same from week to week, or even bottle to bottle.
Please note that I am not talking about adulterated products, such as the herbal treatments for impotence that were found to contain pulverised Viagra tablets. I'm talking about the natural variability of plant products. Can I be sure that what I am taking is both what it says on the label and is the same every time I take it?
Some research has just been published about the varieties of plant products found in herbal medicines. This research used DNA testing to separate out the various components found in some preparations.
I'll let the author's speak for themselves. Here is a slightly edited version of the abstract of their published paper.
Herbal products available to consumers in the marketplace may be contaminated or substituted with alternative plant species and fillers that are not listed on the labels. According to the World Health Organization, the adulteration of herbal products is a threat to consumer safety. Our research aimed to investigate herbal product integrity and authenticity with the goal of protecting consumers from health risks associated with product substitution and contamination.
We used DNA barcoding to conduct a blind test of the authenticity for 44 herbal products representing 12 companies and 30 different species of herbs, and 50 leaf samples collected from 42 herbal species.
We recovered DNA barcodes from most herbal products (91%) and all leaf samples (100%), with 95% species resolution using a tiered approach. Most (59%) of the products tested contained DNA barcodes from plant species not listed on the labels. Although we were able to authenticate almost half (48%) of the products, one-third of these also contained contaminants and or fillers not listed on the label. Product substitution occurred in 30/44 of the products tested and only 2/12 companies had products without any substitution, contamination or fillers. Some of the contaminants we found pose serious health risks to consumers.
Most of the herbal products tested were of poor quality, including considerable product substitution, contamination and use of fillers. These activities dilute the effectiveness of otherwise useful remedies, lowering the perceived value of all related products because of a lack of consumer confidence in them.
If this level of quality control was present for all the packaged foods we buy there would be outrage, legal action, bankrupt companies and executives in prison. Consumers complain that the corn flakes they bought this week are a slightly different colour to last week's, but at least they know the same recipe was used both times. If pharmaceutical companies worked like this people would be dying.
it's bad enough that the makers and sellers of snake oil don't have to prove that it works. I don't think it's unreasonable to demand that at least we should be able to trust that what we get is what is on the label, at the concentration stated on the label, and nothing that is not on the label.
Maybe I'm too optimistic.
DNA barcoding detects contamination and substitution in North American herbal products, Steven G Newmaster, Meghan Grguric, Dhivya Shanmughanandhan, Sathishkumar Ramalingam and Subramanyam Ragupathy; BMC Medicine 2013, 11:222
This article was published as the Naked Skeptic column in the January/February 2014 edition of Australasian Science
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