Understanding the Comfrey Controversy: Humans vs. Plants
Comfrey's reputation is split dramatically between human medicinal use and gardening applications. While ancient civilizations used it extensively for healing, modern science has uncovered a serious toxicity risk that makes comfrey tea and other internal preparations dangerous for humans.
The root cause of this risk lies in naturally occurring compounds called pyrrolizidine alkaloids (PAs), which are potent hepatotoxins. When ingested, these PAs can cause severe and irreversible liver damage, a condition known as hepatic veno-occlusive disease. For this reason, health authorities in many countries, including the US Food and Drug Administration (FDA), have banned oral comfrey products.
This stands in stark contrast to its undeniable benefits in the garden. Comfrey is a dynamic accumulator, meaning its deep taproots draw up a wealth of nutrients from the subsoil, such as potassium, phosphorus, and nitrogen, concentrating them in its leaves. Gardeners can harness this nutrient bounty safely by making comfrey tea for plants, a process that creates a highly effective liquid fertilizer.
Making Comfrey Tea for the Garden
Creating comfrey tea for your garden is a straightforward process that provides your plants with a potassium-rich feed, perfect for fruiting and flowering plants like tomatoes and peppers. It is important to note that this is an organic fertilizer meant only for garden use, not for human consumption.
Step-by-Step Instructions:
- Harvest comfrey leaves: Cut mature leaves and stems from established comfrey plants, using gloves to protect your hands from the fine hairs. Russian comfrey (Symphytum x uplandicum 'Bocking 14') is a popular sterile variety for this purpose.
- Fill a container: Pack the chopped comfrey leaves tightly into a large bucket or barrel. Filling it about two-thirds full is ideal.
- Add water and seal: Add water to cover the leaves completely and place a weight on top to keep them submerged. Secure the container with a lid, as the fermentation process will produce a very strong, unpleasant odor.
- Wait and ferment: Allow the mixture to steep for 4 to 6 weeks. The liquid will turn a dark, greenish-brown color.
- Dilute and apply: Draw off the resulting liquid and dilute it with water before applying. A common ratio is 1 part comfrey tea to 10 parts water, but some gardeners recommend starting weaker, at 1:15, and increasing gradually to avoid burning plants.
Internal vs. External Human Use
Historically, comfrey was ingested as a tea or capsules to treat various internal ailments, from stomach issues to bronchial inflammation. Today, due to the high risk of severe liver damage from pyrrolizidine alkaloids (PAs), oral ingestion is strictly advised against by medical professionals and regulatory bodies.
In contrast, some external use of comfrey preparations is still considered potentially safe, provided it is applied correctly. Comfrey ointments or creams may be used on unbroken skin for a short period (generally no more than 10 days) to treat muscle and joint pain, as well as minor bruises and sprains. The PA absorption through the skin is generally considered low, but the risk of toxicity remains if applied to broken skin or used for extended periods. The active compounds, such as allantoin and rosmarinic acid, are thought to contribute to its anti-inflammatory and wound-healing effects. However, even external application carries some risk, and many health professionals still caution against any use.
The Verdict: Comparing Comfrey Tea Uses
| Feature | Internal Use (For Humans) | External Use (For Humans) | Gardening Use (For Plants) |
|---|---|---|---|
| Toxicity Risk | HIGH. Contains hepatotoxic pyrrolizidine alkaloids (PAs) that can cause liver damage and cancer. Oral products are banned in many countries. | LOW to MODERATE. Possible PA absorption through broken skin, not recommended for prolonged use or open wounds. | NONE. Safe and effective as a nutrient-rich fertilizer for plants, not for human consumption. |
| Primary Benefit | Historically used for internal healing, but benefits are unproven and far outweighed by severe health risks. | Potential anti-inflammatory and pain-relieving effects on unbroken skin for short periods. | High in potassium and other nutrients, promotes flowering, fruiting, and overall plant health. |
| Scientific Consensus | Strongly discouraged and legally restricted due to proven toxicity. | Limited studies show some efficacy, but safety concerns remain. Use is controversial. | Widely accepted and used by organic gardeners as a natural, organic liquid fertilizer. |
Conclusion
Ultimately, whether does comfrey tea work depends entirely on its application. For human consumption, the answer is a definitive and dangerous no. The presence of toxic pyrrolizidine alkaloids makes internal use a severe health risk, and regulatory bodies have banned oral comfrey products for good reason. The rumored health benefits for internal issues are not supported by evidence and are overshadowed by the potential for life-threatening liver damage.
Conversely, for the dedicated organic gardener, comfrey tea is a powerful, free, and highly effective tool. As a liquid fertilizer, it provides a valuable boost of nutrients, particularly potassium, to flowering and fruiting plants, significantly improving their health and yield. The key is understanding and respecting the plant's dual nature: a potent poison for the liver and a nurturing tonic for the garden.
External Link for Further Reading
You can read more about the toxicity of pyrrolizidine alkaloids on the NCBI Bookshelf.
