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.