10. Symphytum officinale use has low incidence of hepatic problems.
Human Toxicology, PC Anderson and AEM McLean
Hepatotoxic effects of Symphytum officinale questioned in clinical setting.
The Laboratory of Toxicology in London, sent volunteers a questionnaire regarding how long they had used comfrey and the amount and form in which the herb was taken. At the same time the participants underwent liver function tests at the local hospital. There was a considerable variation in how the herb was taken and in what form. Nonetheless, results of the tests were found to be within the normal range with the exception of a slight elevation in bilirubin levels in two of the participants. There was no evidence of liver injury in this sample, even for those who had consumed the herb for twenty years.
Comfrey is safe when consumed in its whole state. The people in this study were repeat consumers of comfrey for long periods of time without ill effects.