Russian comfrey ($$Symphytum \times uplandicum$$), a hybrid of common comfrey ($$Symphytum officinale$$) and rough comfrey ($$Symphytum asperum$$), is widely known in permaculture and herbalism, but its internal use is extremely dangerous. The primary danger lies in its high levels of pyrrolizidine alkaloids (PAs), which are potent hepatotoxins. These compounds can cause severe and irreversible liver damage when ingested, leading to a condition known as hepatic veno-occlusive disease (HVOD). Health regulators worldwide, including the US Food and Drug Administration (FDA), have banned oral comfrey products due to these risks.
The High Cost of Eating Russian Comfrey
Many people are familiar with comfrey as a garden plant, a powerful fertilizer, or a historical remedy, but they may be unaware of the critical distinction between its external and internal uses. The toxic PAs present in the plant are not destroyed by cooking, and they accumulate in the body over time, making even small, repeated doses extremely harmful. The concentration of PAs varies depending on the plant part and its age, with roots containing significantly higher levels than leaves. Russian comfrey, in particular, is noted for containing higher concentrations and more toxic forms of these alkaloids than common comfrey.
Risks of Internal Comfrey Consumption
- Liver Failure: The PAs in comfrey are metabolized in the liver, where they create toxic intermediates that can cause HVOD, a blockage of the small veins within the organ. This can rapidly lead to liver failure and, in some cases, death.
- Carcinogenic Properties: Animal studies have shown that ingesting comfrey can lead to liver tumors, indicating its carcinogenic potential. The genotoxic effects of PAs—their ability to damage DNA—are a primary concern.
- Other Toxicities: Beyond the liver, PAs can cause damage to other organs, such as the lungs, especially with high doses.
How Toxicity Affects Different Body Parts
- Digestive System: Initial symptoms of PA poisoning can include abdominal pain, nausea, and fluid retention (ascites), as the liver struggles to function.
- Skin and Surface Use: While oral consumption is strictly prohibited, the external application of comfrey ointments and creams on unbroken skin is considered possibly safe for short periods. The compounds help with wound healing and pain reduction, but care must be taken to prevent systemic absorption. Do not apply to open wounds.
The Dangers of Mistaken Identity
Herb identification is critical, and a misidentified plant can have fatal consequences. Foxglove ($$Digitalis purpurea$$), a highly toxic plant, can be confused with comfrey due to similar-looking leaves before flowering. Ingesting foxglove can lead to heart damage and death due to cardiac glycoside poisoning. Always be certain of the plant's identity and avoid internal use of any comfrey species due to the inherent risks.
Russian Comfrey vs. Common Comfrey: A Toxic Comparison
Although both species contain toxic pyrrolizidine alkaloids, the concentration and type vary, making Russian comfrey even more dangerous for ingestion.
| Feature | Russian Comfrey ($$Symphytum \times uplandicum$$) | Common Comfrey ($$Symphytum officinale$$) |
|---|---|---|
| Key Alkaloids | Contains echimidine, considered one of the most toxic comfrey PAs. | Contains PAs like intermedine and lycopsamine, which are less toxic than echimidine. |
| Alkaloid Concentration | Generally contains higher levels of toxic alkaloids in its roots and leaves. | Contains lower levels of PAs, especially in the leaves. |
| Edibility Recommendation | Strictly advised against internal use due to high toxicity and concentration of potent alkaloids. | Also advised against internal use due to cumulative liver damage potential, despite lower PA content. |
| Agricultural Use | Popular, sterile hybrid (like Bocking 14) used primarily for fertilizer and animal fodder, not human consumption. | Also used for compost and medicine, but still carries internal risks. |
Conclusion: A Clear Warning Against Ingestion
Despite a long history in traditional medicine, scientific evidence unequivocally demonstrates that eating Russian comfrey is unsafe. The presence of hepatotoxic pyrrolizidine alkaloids, especially the highly toxic echimidine, poses a significant risk of liver damage and cancer. Health agencies and toxicologists worldwide advise against any internal consumption of comfrey, regardless of the species or how it is prepared, as cooking does not eliminate the risk. The risk of cumulative damage makes even small, repeated doses hazardous over time. For those seeking the traditional therapeutic benefits of comfrey, modern medicine and herbalists now advocate for strictly controlled, short-term topical applications on intact skin, while avoiding any oral intake. For information on comfrey safety and regulation, consult the U.S. National Institutes of Health via their LiverTox website.
