Comfrey’s uses come with risks

The fuzzy leaves of the blue-flowered comfrey plant contain allantoin, a protein that stimulates cell growth and has long been thought to help broken bones heal. The plant also contains pyrrolizidine alkaloids, toxic chemicals that are highly concentrated in its roots.

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Uses: Comfrey is taken in a variety of ways, some more dangerous than others. Oral preparations are used for stomachaches, ulcers, respiratory infections and diarrhea. Mouthwash made from its roots is used for sore throat and gum conditions, and topical ointments can treat bruises, sprains and joint pain.

Dose: Medical experts in this country discourage all but comfrey leaf ointments. Those should be applied to unbroken skin, but for no more than two to four weeks.

Precautions: Pyrrolizidine alkaloids can cause liver damage and cancer. The German government has ruled that recommended doses of commercial comfrey preparations provide no more than a microgram of pyrrolizidine alkaloids per day. Because oral comfrey supplements are not standardized or monitored in the U.S., they should be avoided -- especially by people with liver disease, children and the elderly. Topical comfrey may cause sleepiness and stomach pain.

Research: Oral comfrey has caused liver damage and cancerous growths in animal studies. In humans, it has caused liver failure and, in a few cases, death. Comfrey ointments can be effective when used to reduce pain and heal swelling and probably are safe when used in moderation on unbroken skin.

Dietary supplement makers are not required by the U.S. government to demonstrate that their products are safe or effective. Ask your healthcare provider for advice on selecting a brand.

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-- Elena Conis