The Real Reason Comfrey Tea Was Banned In The US

As a flower, comfrey is deceptively beautiful: long, slender, and imbued with elegance akin, almost, to the bluebell. As an herb, it's ancient enough to count at least ten names: comfrey, knitbone, boneset, ass ear, black root, blackwort, bruisewort, salsify, slippery root, and wallwort (via Very Well Fit). Ancient Greeks and Romans apparently used comfrey to heal. Depending on who you ask, comfrey transforms into a kind of magical, miracle drug, to treat bronchitis, peptic ulcers, diarrhea, rheumatoid arthritis, and acne. Some say it reduces scars, improves circulation, and heals broken bones and sprains. And, the herb may as well have certain healing properties. Limited medical research suggests that comfrey has, in some circumstances, successfully treated muscle inflammation and swelling.

And yet, if the ancient Greeks and Romans used comfrey as a medicine, at least in the form of a tea, it appears that it was doing much more harm than good. In 2001, the Food and Drug Administration voiced its "serious concern" about the use of comfrey in dietary supplements, citing "serious adverse incidents" due to their consumption. The regulatory agency has since banned oral comfrey products, including comfrey tea, completely (via Penn State Milton S Hershey Medical Center).

Could drinking comfrey tea cause cancer?

In 2001, when the US Food and Drug Administration first rang alarm bells about comfrey products, they warned that the pyrrolizidine alkaloids in comfrey could not only cause "liver damage" but were also "possible carcinogens." Back then, Relias Media interviewed herbalist and botanist Christopher Hobbs, who called the FDA's proclamation an overreaction and questioned the validity of the research the agency cited. "Millions of people have used comfrey and there have only been a few reports of adverse events," Hobbs pointed out. "If the safety issue is all that serious, why didn't they take this action sooner?"

Our advice? Don't be so quick to take Hobbs at his word. Since 2001, clinical research on drug-induced liver injuries has correlated "acute liver injury resembling sinusoidal obstruction syndrome" to the consumption of comfrey either in tablet or tea form (via LiverTox). In 2018, further research suggested that the s 14 pyrrolizidine alkaloids found on comfrey "interact" with the liver in such a way as to damage the liver's DNA, mutate it, and cause cancer.