Subject: comfrey toxicity

From: [email-masked] (Stuart Krasnoff)
Date: Fri, 20 Jan 1995 15:33:13 +0000

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.  Abundant human case studies, often poisonings
by herbal or 'bush' teas made from plants containing these alkaloids, are
consistent with evidence from animals.
	England, Canada, and Germany have banned the sale of comfrey and products
containing it.  Comprehensive reviews on the subject can be found in
"Toxicity of comfrey" by K.A. Winship (Adverse Drug Reactions and
Toxicological Reviews 1991 Vol. 10: 47-59) and Comfrey: Assessing the
low-dose health risk" by Peter J. Abbott (Medical Journal of Australia,
1988, Vol. 149: 678-682).

---

From: [email-masked] (Conrad Richter)
Date: Sat, 21 Jan 95 17:33:46 EST

[email-masked] (Stuart Krasnoff) writes:

> 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 
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 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.  

RICHTERS HERBS                     | Info:                 [email-masked]
Goodwood, ON  L0C 1A0, Canada      | Catalog Requests:  [email-masked]
Tel +1-905-640-6677  Fax 640-6641  | What's New for '95:    [email-masked]