Is Comfrey Safe to Feed Your Birds?

By
Alicia McWatters, Ph.D, C.N.C.

Comfrey has been used as a healing herb since at least the Roman times. Comfrey’s constituents are: mucilage, allantoin, (up to 0.8 %), pyrrolizidine alkaloids, tannins, resin, essential oils, carotene, glycosides, beta-sitosterol, and steroidal saponins, triterpenoids, vitamin B12, C, E, protein (up to 33 %), potassium, iron, silica, zinc and other mineral salts. It is used in the form of fresh leaves in salads, dried leaves for tea, and the root may be ground to produce a powder (the most potent form), which contains about ten times the concentration of pyrrolizidine alkaloids found in the leaves.

Comfrey has been successfully used in treating wounds, aiding in digestive irritation (passing through if there is nothing to heal), and while it contains a fair amount of silica, is useful in the stimulation of bone, connective tissue and cartilage repair. It is also valued as a demulcent herb rich in complex mucilage materials, which can soothe inflamed mucous membranes, and improve respiratory disorders.

Recently there has been concern that the pyrrolizidine group of alkaloids contained in comfrey may cause liver damage. This group is hepatotoxic, causing in the liver either acute reactions or slower chronic symptoms of wasting with the development of extensive liver tumors according to the amount and duration of ingestion. However, this degeneration has only been shown with high doses of plant extract and not with usage of whole herb in sensible amounts. These alkaloids are organic substances and as a group they are very diverse in structure. They are derived from amino acids, have nitrogen in their structure and have marked physiological activity. Chemically they are divided into 13 groups based upon their structure, and the activities they show are as diverse as these structures. There are alkaloids that act on the liver, the nerves, the lungs, and the digestive system. Many of the most valued herbs contain these potent chemicals. It is worth remembering that the stimulant action of tea and coffee comes from several alkaloids and that the white latex in the leaves and stems of lettuce contains alkaloids.

Aviculturists have used comfrey over a span of many decades, as a source of nutritional food for their birds. Symphytum officinale (common comfrey) belongs to the plant family Boraginaceae. There are two other separate species recognized as far more harmful than the former, known as Russian comfrey, S. x uplandicum Nym. and S. asperum Lepech., also known as prickly comfrey.

In view of the controversy regarding this plant, we should identify the species of comfrey we use and then offer only rationed amounts of the common species (Symphytum officinale) in our birds' diets. Or, eliminate it completely until more scientific data is available. But, like many other things in life, moderation is usually your best choice, even with those foods considered very safe.

NOTE: The greatest concentration of pyrrolizidine alkaloids is in the seeds and flowers.

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