Comfrey a highly esteemed herb
Some think comfrey is a panacea useful to heal wounds, broken bones against varicose veins, cough, cancer, high blood pressure to name a few. Comfrey is a herb which was held in high esteem throughout history by ancient and modern herbalists alike: Dioscorides, Paracelsus, the Australian herbalist like Isabelle Shipard or the Austrian herbalist, Maria Treben all praise this herb.
Some people even eat comfrey in soups, fritters or other recipes.
However, in 1984 comfrey was prohibited and Australia’s National Health and Medical Research Council placed it on the nation’s Poison Advisory list. In 2001, the United States Food and Drug Administration issued a ban of comfrey products marketed for internal use and a warning label for those intended for external use. Comfrey is no longer sold in the U.S., except in creams or ointments. The United Kingdom, Canada, and Germany also have banned the sale of oral products containing comfrey.
There is more than just one comfrey
The Latin name of the comfrey family is Symphytum. Most common forms found in gardens are the common comfrey S. officinale and the Russian comfrey, S. x uplandicum, a cross between the common comfrey and rough comfrey, S. aperum.
Comfrey plants are a member of the borage family. Most comfrey sold in Australia, even when marked as S.officinalis are Russian comfrey plants. It is quite likely that your official or common comfrey in your garden is the Russian one.
The poison in comfrey
The reason is that comfrey contains Pyrrolizidine alkaloids, in short PA’s.These alkaloids have shown to cause a disease where the small and medium veins of the liver become obstructed, which results in liver dysfunction, cirrhosis and possibly death. The disease is called veno-occlusive disease. There are several PA’s found in all varieties of comfrey, echimidine, being the most toxic one is mainly found in Russian comfrey, but there are conflicting studies on that.
The ban of comfrey is based mainly on two research studies:
The first study was ‘Carcinogenic activity of symphytum officinale’ by Hirono, Mori and Hago in 1978, Japan. Comfrey leaves and roots were ground and added to the diet of 4-6 week old rats. Leaves were added at 8-33% of their diet and roots at 1-8% of the diet for 179 to 600 days. All diet groups showed an increase in liver tumours over controls. 96% of the liver tumours detected 96% were benign, that means that they were not cancers.
Criticism arose because of the high levels of comfrey the rats had to eat, which would be far over the normal medicinal dose for humans.
The second study was called ‘The Structure and toxicity of the alkaloids of Russian comfrey (S. x uplandicum) a medicinal herb and item of human diet’ by Dr. C. Culvenor, et al, Australia, 1980′. Baby rats were injected with PA’s extracted from the Russian comfrey. Liver damage occurred in higher doses. Russian comfrey contains several times the amount of PA’s than common comfrey so why was Russian comfrey used? Herbalists point out that there is a huge difference between the whole herb and the use of single chemicals extracted from that herb, the study works with the single chemical which is injected instead of eaten. The dosis in this study was so high that it could never been reached by normal consumption.
Many people take comfrey on a daily basis, but only four somewhat questionable cases have been found worldwide where people were harmed due to the use of comfrey between 1985 and 1990. The reports are spotty and preexisting illnesses, other drugs or extremely high doses might have been the culprit.
PA’s in leaves were found much lower than in roots.Small young leaves show higher concentrations of PAs than larger leaves in later stages of the growing season.
My five cents:
Comfrey is such an important herb through the ages that it deserves a bit more scientific attention than studies from bygone times. How comes that a study is even published and used to justify laws, when not even the right species is used? Why do studies use extract instead of herbs, while the common use of comfrey was the herb and not the extract? Why is no study undertaken of people who are already using comfrey?
Of course, only because a herb was used over a long time does not mean that it is not toxic. Who knows weather people died from using comfrey, liver toxidity may show up only years later. In the past, most people had real knowledge of herbs not internet knowledge and often herbs were used in a very specific manner which might have lessen their toxicity.
I would like to know more about comfrey. Are there more recent studies? Do you use comfrey? What is your opinion?