6. Symphytum officinale has been clinically proven not to have carcinogenic effects.
Ames, B. PhD. et al. 1987. Science 236:271
Study of carcinogenity of naturally occurring and man made substances. Comparative risk assessment.
Dr. Bruce Ames determined in his clinical study that a water infusion (tea) made from Symphytum officinale had the same carcinogenic effect as 1 peanut butter sandwich (aflatoxin), ½ the risk of consuming a raw mushroom (hydrazine), ½ the risk of consuming a diet soda containing saccharin. And about 1/100 of the risk of consuming a standard beer or glass of wine (ethyl alcohol). Dr. Ames also estimated that comfrey/pepsin tablets carry up to 200 times the risk of comfrey tea.
Symphytum officinale is as safe as many common food items.