The following release was posted on the American Association of Feed Control Officials (AAFCO) web site.
During the AAFCO Annual Meeting in August 2002, the Enforcement Strategy for Marketed Ingredients (ESMI) Working Group announced the target ingredient recommended for a future regulatory enforcement event. The target ingredient, comfrey, has been shown to be a health and safety concern for animals and humans, prompting regulatory action by the United States, Canada, and Germany. Comfrey does not meet any of the recognized criteria for use as an animal feed ingredient or animal feed.
Comfrey was identified by the ESMI Working Group based on the following published scientific information provided by the United States Food and Drug Administration (FDA), Center for Veterinary Medicine with references provided at the end of this document:
The leaf and root of the comfrey (Symphytum officinale) plant have been used in supplements. Supplement use has been orally for ulcers, diarrhea, cough, bronchitis, and rheumatism, or topically for the treatment of inflammation, arthritis, wounds, and bruises. This supplement has been banned in Germany and Canada due to safety concerns.
Comfrey has shown to be hepatotoxic (relating to or causing injury to the liver) in both humans and rats. The toxic compounds found are pyrrolizidine alkaloids (eight have been identified), which include lasiocarpine and symphtine. The highest content of these substances were found in products containing bulk comfrey root or leaf.
Pyrrolizidine alkaloids have also been associated with lung and liver cancer. The primary liv