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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Sunday 15th April 2012

In the past week, I’ve written twice about how aristolochic acid (AA) from plants in the Aristolochia genus has been shown to cause upper urinary tract cancer. The continuing presence of AA in Traditional Chinese Medicine (TCM) remedies, in spite of its being banned both in Taiwan and many importing countries, has broadened the debate about potential harm to include the full range of herbal preparations.

By coincidence, this week also saw the publication of a ‘Research Article’ from Australia1 looking at a wider range of TCM preparations.

I’ve mentioned before the frustration I feel when researchers, who are, after all, supposed to be asking questions to get at new knowledge, will often make statements in the introductions to their papers that do not stand up to scrutiny. This is most often seen when research into ricin, the poisonous component of Ricinus communis, the castor oil plant, states in the opening paragraph that ricin is a powerful bioterror weapon when it is nothing of the sort.

Coghlan et all do the same with the opening sentence of their article;

‘Traditional Chinese medicine (TCM) has been practiced for thousands of years’

That is stated as though it were a universal truth but, as I mentioned in February, there are those who say that TCM was an invention of the newly established Communist regime and that Chinese traditional medicine is, to a debatable extent, based on the work of Hippocrates. Dr Paul Unschuld says that two strands of thought about health developed in China and the most effective elements of both were brought together to create TCM2,3.

This may seem trivial but its importance lies in the fact that it gives a defence to proponents of TCM who can argue that ‘everyone’ accepts that it is thousands of years old so why has it not been found to be harmful before. It is true, of course, that the Chinese must have been taking some medication throughout history but, not necessarily, the substances marketed today as TCM.

Of course, the ‘it has been used for a long time’ defence is not unique to TCM. It falls down on two grounds and to illustrate both of them I’ll refer, again, to Aristolochia clematitis.

Aristolochia clematitis, birthwort

Aristolochia clematitis, birthwort

First, we really don’t know what people died from in the past. They just died. Aristolochia clematitis, birthwort, was widely used in childbirth because of the Doctrine of Signatures. We know that death in childbirth was a common occurrence in the past but we can’t say how much of that can be attributed to the destruction of the kidneys by aristolochic acid.

And, secondly, people died of other things in the past. The condition known as Balkan endemic nephropathy (BEN) (now renamed aristolochic acid nephropathy (AAN)) did not become visible until the second half of the 20th century because it takes a long time to develop, if the dose of AA is small, and people died of other things before end stage renal disease could set in.

To be fair to Coghlan et al, their article is not really about TCM itself, though you might not realise that from the majority of the media coverage; it is a demonstration of a method that might, with further development, provide a rapid and convenient way for border agencies to identify the contents of material being presented for import.

The research is, therefore, only concerned with 15 samples and it is likely that gainsayers will claim that this indicates that the overwhelming number of products is OK. What the research is concerned with is demonstrating that ‘second-generation, high-throughput sequencing (HTS) of DNA’ can provide quick reliable answers to the question ‘What is in this?’ At present, it is necessary to decide what you think is present and test for that. This new technique allows for the identification of all contents.

Aristolochia clematitis, birthwort

Aristolochia clematitis, birthwort

Even with only 15 samples, however, the research shows that TCM substances very frequently contain material that is not declared on the packaging and, sometimes, that material is toxic.

The technique involves determining all the DNA sequences in the sample and comparing these with database references to identify them. As the researchers note, at the moment, the database information for animals is much greater than for plants so, while they were able to identify specific species of animals in the material tested, they were only able to identify plants at the family level for the most part.

At the genus level, they were able to identify Aristolochia and Ephedra because more work has been done on these plants. Ephedra has been banned in the USA since 2004 as a result of evidence of adverse effects and deaths resulting from its use as an herbal remedy.

The paper concludes that, for the technique to be widely useful much more research needs to be done on the DNA sequences found in plants but it believes that this work should be done given the very worrying results from a very small sample of products.

There has been quite a lot of coverage of this report but, as is often the case, NHS Choices4 provides a clear analysis and assessment.

I’ll finish by pointing out that the pharmaceutical industry had no input into this research so when the argument is trotted out, as it may well be, that this is just another attempt to protect the profits of multinationals against ‘natural’ remedies you will know that this is not the case.


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