Comfrey herb tea and liver disease

Nutrition Research Newsletter, May, 1989 by P.M. Ridker, W.V. McDermott

COMFREY HERB TEA AND LIVER DISEASE

Hepatic veno-occlusive disease is a potentially fatal cause of liver failure, usually attributed to exposure to plants that contain toxic pyrrolizidine alkaloids. Although it is commonly thought that ingestion of these alkaloids is not a problem in developed countries, cases of hepatic veno-occlusive disease have been reported from the United States, the United Kingdom, and Switzerland, and at least two of these cases have been linked to the consumption of the commercially-available herb comfrey. A report in The Lancet notes that despite past warnings about toxicity, comfrey products continue to be marketed as herbal teas, herb root powders, and capsules. Toxic levels of alkaloid have been found in commercial preparations. Pyrrolizidine alkaloid poisoning is difficult to diagnose; it may be necessary to obtain and analyze herbal preparations used by the patient in order to discover the cause of liver failure. "Physician and consumer awareness of herbal toxicities is extremely limited, and the incidence of hepatic veno-occlusive disease and of pyrrolizidine poisoning may be grossly underestimated."