Comfrey toxicity.

Newsgroups: alt.folklore.herbs
Subject: Re: comfrey toxicity
From: (Conrad Richter)
Date: Sat, 21 Jan 95 17:33:46 EST (Stuart Krasnoff) writes:
> Here's a piece of a letter I wrote to a local paper in response to an article advocating the use of comfrey. Email me if you want more references.
> Anyone who's considering ingesting comfrey or anything derived from it should to be aware that this plant, as well as virtually all members of the plant family Boraginaceae (e.g. borage, forget-me-not, heliotrope) that have been analyzed, contain pyrrolizidine alkaloids (PAs) , often in relatively high concentrations (approaching 0.5% dry weight in comfrey roots). Other plants that may be familiar to herbalists like the Joe Pye Weeds (Eupatorium purpureum and maculatum), Boneset (Eupatorium perfoliatum), Common groundsel (Senecio vulgaris), and Coltsfoot (Tussilago farfara) also contain PAs.
> A wealth of experimental evidence shows that PAs cause a variety of acute toxic effects in animals, most notably irreversible liver damage. They also cause mutations and cancer in laboratory animals, can cross the placenta and also are excreted into milk with liver damage observed in fetal animals and sucklings.

Some PAs including some found in comfrey actually have anti-tumour effects also. And veno-occlusive disease is not necessarily irreversible; this was proven in poisoning cases in India.

Nevertheless, most of the above is true, but....

> Abundant human case studies, showing poisonings by herbal or 'bush' teas made from plants containing these alkaloids, are consistent with evidence from animals.

.... is not true, there are not very many case studies concerning comfrey, certainly nothing compared to the extent to which it has been ingested both for nutritional and medicinal reasons.

The problem with comfrey is more a case of its being promoted for non-traditional purposes in the 1960s and 1970s. Lawrence Hills of the Henry Doubleday Research Assocation was a big proponent of its use as a nutritional aid, mainly because it has high protein and B12 content. Mr. Hills was very interested in low cost, high quality food sources for the Third World and he thought comfrey was a godsend for the poor peoples of the world. He was devastated by the reports of its liver-toxicity and gradually moved his organization away from comfrey to other crops.

But the message of comfrey's nutritional value had taken hold in England and North America. People were eating leaves or drinking teas daily for this reason. But this not a traditional usage of the plant. Traditionally it was used internally for acute problems like ulcers, or used as a poultice or ointment externally for skin problems, chronic ulcers and broken bones. In fact, its use in these ways date back hundreds, if not thousands of years.

Frankly, I think comfrey got a bum deal. It got lumped in with other far more dangerous PA-containing weeds that contaminate cereal crops and grazing lands. These are plants like Heliotropium, Senecio and Crotalaria which have caused poisoning in India, Afghanistan and South Africa among other places. If comfrey use is restricted to its traditional usage -- usage for acute problems or for external skin problems -- then none of paranoia that exists today would have developed.

That's just a hunch.

I should point out that I have a vested interest in this matter: I sell comfrey plants, seeds, dried herb and ointment.

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