Wild Ginger (Asarum canadense) and Aristolochic Acid
Answered by: Conrad Richter
Question from: Wendy Applequist
Posted on: March 13, 2002

This is not quite an inquiry, but I don’t know where else to direct it. I wish to call attention to the fact that your catalog’s description of wild ginger (Asarum canadense) contains an inaccuracy that could be used to cause trouble for you. The catalog states, "Has anti-tumour compound aristolochic acid." This bit of information keeps appearing in books on edible and medicinal plants, including the Peterson field guide, which may be where you got it.

As it happens, there is some good evidence that the aristolochic acids in Aristolochia species may cause often severe kidney damage when consumed long-term. This has been termed "Chinese herbs nephropathy," and though certain people would like to see it everywhere, it does appear that at least in susceptible people, aristolochic acids are quite toxic. Kidney disease associated with consumption of various species has been reported worldwide. In fact, there has been some suggestion that it also causes kidney cancer; this comes from a famous case unfolding over the past ten years in which up to a hundred women who were apparently given Aristolochia fangchi at a Belgian weight-loss clinic were permanently injured (dozens suffering dialysis or transplant). As it happens, the paper "demonstrating" that aristolochic acid also caused kidney cancer in many of these women is weak; it appears equally likely that a separate single compound which was included in their complex program acted synergistically with the aristolochic acid, and kidney cancer is not reported elsewhere as a sequel to aristolochia nephropathy; but for political reasons the medical profession may not wish to hear such arguments. Yes, aristolochic acid did show anti-tumour effects in some early studies, but this is true of many compounds that are just plain poisonous and will kill everything in the petri dish, and you do not want to encourage the consumption of such things.

Our FDA has banned everything said to contain aristolochic acids, including wild ginger, from the food and dietary supplement market. As it happens, I’ve worked on a project to collect A. canadense and related species all over the U.S.A. so that they might be screened for aristolochic acids (MS submitted to Pharmazie). It turns out that one form of aristolochic acid is indeed present in wild ginger. Quantities can vary a hundredfold, ranging from below the limit of quantification to 10% or more of the amount found in some Aristolochia species. Specimens from the Northeast and stressed habitats were highest.

Now, I believe that few or no people have ever actually gotten sick from consuming Asarum. However, a general rule food safety experts use is that the amount of a toxic chemical that is allowed into food should be no more than 1% of the amount believed to make people sick (to account for variations in individual tolerance, consumption, and so forth). By this standard, wild ginger flunks. Since it is often prepared candied, one might eat quite a lot of it over months or years, and consuming the same quantity of an Aristolochia species *would* be dangerous, probably causing kidney failure in some percentage of users. Since Asarum can contain a significant fraction of the aristolochic acid I in Aristolochia, prudence would suggest avoiding its regular consumption. (I am a fan of wildcrafting, but I would not be comfortable eating this stuff, especially from the NE, knowing what I know now.) I don’t suggest that you stop selling it altogether – it does have historical, ethnobotanical uses of interest, for one thing, and it makes a cool ground cover – but you really should not be using the aristolochic acid content as a selling point for why people should eat more of it. Eventually, someone with an axe to grind will see that and hit the roof.

Well, time to get off the soapbox... Thanks, and best wishes.

Thank you very much for alerting us to the potentially misleading statement about the properties of aristolochic acid in wild ginger. Given the recent spate of regulatory concern about aristolochic acid-containing herbs, we agree that it is not appropriate to promote a potential antitumour effect and we are withdrawing the statement from our catalogue. According to a recent press release from Health Canada (the Canadian regulator of medicines and herbs), "[a]ristolochic acid can cause cancer, changes in human cells and kidney failure."

Notwithstanding the obvious logic that the presence of compounds such as aristolochic acid ought to provoke caution, we are however wary of immediately concluding that all herbs with such compounds are necessarily dangerous or ought never be used. This is a thorny issue because in theory just about every food and herb has some "bad" compound in it. If that is true for wild ginger then the questions that need to be asked are how much of the compound is present, is that amount relevant, are there mitigating compounds, and are there usage rules that mitigate the risks. In the absence of exhaustive research to answer these questions, the regulators simply remove herbs with these compounds and our worry is that eventually many useful herbs will be removed from the market.

The American Herbal Products Association in its "Botanical Safety Handbook" (CRC Press, 1997) says: "Because aristolochic acid is both carcinogenic and nephrotoxic, the plants containing it are not recommended for long-term use. Even though there is an extensive history of use of these plants with no reports of carcinogenic effects, recent events regarding wight loss preparations which contain herbs high in aristolochic acid have raised concerns over toxicity in humans." Perhaps a key is to avoid long-term use, while short-term use for acute medical conditions may be safe.

If, as Health Canada noted recently (2001), there have been no reports of adverse reactions to products containing aristolochic acid in Canada, then we have to wonder just how relevant aristolochic acid is in herbs such as wild ginger. I don’t wish to suggest that the regulators are wrong to exercise caution, but sometimes I wish that more weight be given to the traditional experience with herbs. Our own cursory look at traditional references in our library does not indicate that there has been a historical concern about the use of wild ginger either as a medicinal herb or as a substitute for true ginger. That it has been used for culinary uses for many years of course does not prove that it is safe, but to us at least it is a powerful argument that wild ginger may in fact prove to be safe ultimately despite the presence of aristolochic acid.

We would appreciate receiving a preprint copy of the paper you submitted to Pharmazie, for our files, if possible.

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