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The Myth of the Benign Nature of Herbal Remedies

We have beliefs but other people have superstitions. Furthermore, there seems to be a law of the conservation of superstition: if it does not attach to one thing, it will attach to another. Man does not live by rationality alone.

One superstition among their middle-class, educated, and worried-well patients that most irritates doctors is that "natural" preparations, particularly herbal ones, are necessarily benign. People persist in believing this despite the fact that men (and women) have been poisoning one anther to death with herbal extracts since the dawn of recorded history, and most gardens have enough poisonous plants in them to decimate a countryside. No; if you did a word-association test with "herbal remedy," the chances are that words such as "gentle," "healing," "safe," and "non-toxic" would emerge.

A recent paper in the Proceedings of the National Academy of Sciences links the exceptionally high rate of upper urinary tract cancer in Taiwan with the widespread use there of Aristolochia plants in herbal remedies. Such plants contain a carcinogen, aristolochic acid, that affects the urinary tract particularly.

The observation is not new, but the investigators, both Chinese and American, found cytogenetic evidence of a causative relationship between Aristolochia remedies and carcinogenesis in 151 patients suffering from upper urinary tract cancer.

It was already known that there was an epidemiological relationship between such cancers and the consumption of herbal remedies containing aristolochic acid: the greater the quantity consumed, the greater the chance of developing cancer. And in large parts of the Balkans the high rate of such cancers has been attributable to the consumption of bread prepared from flour contaminated with seeds of Aristolochia. Moreover, in Belgium, there was a brief epidemic of renal failure caused by dieting women who took Chinese herbal medicines containing Aristolochia.

The acid in the remedy binds to the DNA in the cells of the kidney cortex, eventually causing carcinogenic mutations. The evidence of a causative relationship between Aristolochia and cancer of the upper urinary tract is therefore now very strong.

Of course, as with any side effect, one must not only consider its severity but its frequency. Something that happens once in a million cases is of very different significance from something that happens once in a hundred. Even the most familiar and supposedly innocuous drug can sometimes have catastrophic effects. The question is not so much whether or not a drug causes a particular side effect, but whether the risk is worth taking. And this is not a simple calculation, because it depends in part on the severity of what is being treated, whether alternatives exist, etc.; and often there can be no definitive answer. Decisions should be made in the light of information but cannot be made by consideration of information alone.

In Taiwan, the herbal remedy is used for hepatitis, urinary tract infection, rhinitis, dysmenorrhoea, and eczema. Alternatives are available, though in some cases they may not be entirely satisfactory, and the effectiveness of the remedy is not in any case proved. It is very unlikely, however, that it does any possible good done that makes it worth risking the potential harm.

However, I do not expect superstitious belief in the essential benignity of herbal remedies to die in the near future as a result of the paper in the Proceedings. I remember a patient who, hearing foxglove was good for the failing heart, made herself a nice cup of foxglove tea from the foxgloves in her garden. She suffered quite severe poisoning; unhappily, she did not realize that, where medicine is concerned, there could be too much of a good thing, though this has been known for hundreds of years.