Comfrey: Super Healer or Lethal Poison?

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A very persistent stand of comfrey at our camp got me wondering about what it is good for, and why it is now regulated in various countries, including Canada, Australia, Germany,  Japan, and the US. Can a plant with comforting folk names such as Knitbone, Woundwort, Healherb, and All Heal, really be all that bad? Why is comfrey mired in controversy?

I started my search at Herbs Are Special, an excellent place to find out about the plant’s history and constituents. I am going to summarize historical uses, the case against comfrey, and provide some pro-comfrey anecdotes.

Comfrey, what is it good for?

In 50 AD, Dioscorides’ Materia Medica prescribed comfrey to heal wounds and broken bones. Since then, other herbalists have claimed the plant can help heal any body part that is torn or broken. Comfrey roots and leaves contain allantoin, a substance that helps new skin cells grow. It was mainly applied externally until the 1800s. Since then, the list of conditions it has been used to treat has become quite long, according to herbsarespecial.com.

“The leaves or roots applied as a wash, poultice or ointment are used for bruising, sciatica, boils, rheumatism, neuralgia, varicose veins, bed sores, wounds, ulcers, insect bites, tumours, muscular pain, pulled tendons, gangrene, shingles and dermatological conditions.” The list of internal uses includes: “Indigestion, stomach and bowel problems, excessive menstrual flow, hoarseness, periodontal diseases, bleeding gums, thyroid disorders, diarrhea, gastrointestinal ulcers, hernia, glandular fever, coughs, lung conditions, hemorrhaging, cancer, catarrh, anemia, sinusitis, lupus, lowering blood pressure, hiatus hernia, blood purifier, and to ease inflammation of the joints and mucus membranes.” Comfrey leaves are rich in chlorophyll, which has been scientifically proven to help rejuvenate old cells and promote the growth of new ones. The plant also contains allantoin, which increases white blood cells.

Is comfrey harmful?

Despite people’s long history of reliance on comfrey as a healing agent, it has gotten a bad rap since 1978, when a rash of blaring headlines in Australia warned that this popular herb is a killer that causes liver damage and cancer. In 1984, Australia’s National Health and Medical Research Council placed comfrey on the nation’s Poison Advisory list.

Research in that nation, and others, shows that comfrey contains several pyrrolizidine alkaloids. Certain plants, such as heliotropium, seneca, and crotalaria, also contain various PAs. People who ingested leaves or seeds from these plants have gotten ill. However, according to the book, The Safety of Comfrey, by J.A Pembrey, “there appear to be no cases, in medical history or veterinary records, of humans or animals, showing clinical symptoms, of pyrrolizidine alkaloid poisoning from the consumption of comfrey.”

Internal use of comfrey in supplements was banned in the US in 2002, but it may still be sold in external potions. When you read the rationale for FDA’s concern, you will see it is based on indications, not human testing.

What FDA says

“While information is generally lacking to establish a cause-effect relationship between comfrey ingestion and observed adverse effects in humans, the adverse effects that have been seen are entirely consistent with the known effects of comfrey ingestion that have been described in the scientific literature…Taken together, the clear evidence of an association between oral exposure to pyrrolizidine alkaloids and serious adverse health effects and the lack of any valid scientific data that would enable the agency to determine whether there is an exposure, if any, that would present no harm to consumers, indicates that this substance should not be used as an ingredient in dietary supplements.”

The scientific trials

What is the scientific research? In a Japanese study in 1978 (Hirono, Mori, and Hago), comfrey leaves and roots were added to the diet of baby rats for a maximum of 600 days and the rats were examined for tumors. Out of 28 rats fed 8% of their diet as dry weight comfrey, one showed a liver tumor at 600 days, according to herbsarespecial.com.

Judy Collins, RN, has a different angle on the study’s outcome in an eHOW article titled, “What Are the Dangers of Comfrey? “Comfrey contains lasiocarpine. Lasiocarpine is a hepatoxin (liver poison) and a carcinogenic member of the PA family. It interferes with RNA and DNA synthesis within the liver cells. Largely, this information is from the study performed in 1978. Rats ingested comfrey in amounts multiple times their body weight on a daily basis for 1.5 to 1.75 years, and, at the end of the experiment, all the rats in the comfrey group developed a type of tumor known as adenoma, which is a benign growth. Hemangiosarcomas, easily metastasized vascular malignant tumors, were seen infrequently in the comfrey rats. The control group did not develop tumors of any type.”

Another study in 1980 by Dr. C. Culvenor’s research team in Australia, injected the suspect alkaloids into the peritoneal cavity of baby rats. To reproduce a comparative dose of the alkaloid in a human a person would have to consume approximately 19,880 leaves, according to herbsarespecial.com.

Trials undertaken in 1983 by Dr. S. J. L. Mount of the Henry Doubleday Association in the UK, concluded that comfrey helps relieve pain. Mount supervised testing of 90 members with osteoarthritis and rheumatoid arthritis who took 4 cups of comfrey tea or 9 tablets daily. Participants experienced no side effects or symptoms of liver problems, but 23-35% said they felt pain relief and improved mobility. Henry Doubleday had become interested in comfrey’s benefits in the 1800s. He founded  his association after observing numerous successful applications of comfrey as stock food and medicine.

When forty long-term comfrey consumers were subjected to liver function tests in another Henry Doubleday Association trial, all were found perfectly healthy, according to Dr. Clare Anderson, from the Laboratory of Pharmakinetics and Toxicology, School of Medicine, University College, London.

Dr. MacAllister at Liverpool University Hospital, became interested in the allantoic acid of comfrey leaf and root as a treatment for cancer. After the restriction of comfrey in the UK, he asked his local Member of Parliament for research that showed comfrey to be a toxic substance justifiably restricted as a deadly poison. “He received 350 pages on pyrrolizidine alkaloids, with a World Health Organisation insignia, dated 1988. However, the information contained very little that was relative to comfrey, but mainly of other species of plants that contained other alkaloids,” according to Herbs Are Special. “Over 200 PA’s, are found in plants, mainly in the Asteraceae, Boraginaceae, and Fabaceae families. The most acutely toxic PA’s, are in plants of the senecio and crotalaria genus. The kind of PA’s found in comfrey are generally considered to be less toxic, however, they must still be regarded as having the potential for liver damage, at even low levels.”

WebMD.com says comfrey is commonly used to treat ulcers, heavy menstrual periods, bronchitis, cancer and chest pain, but there is “little proof” of its efficacy. The site goes on to say that comfrey presents a high risk that can cause serious, and often fatal, complications, including, kidney and liver failure, liver disease, and death.

Testimonials from grassroots comfrey users

Elderly woman corrects anemic blood with comfrey. Emsie du Plessis, 78, was among the comfrey eaters in the Doubleday trials conducted by Dr. Clare Anderson. After feeling weak and dizzy in her garden one day, she went to the doctor who said she was a bit anemic. Ms du Plessis began consuming three to four leaves of raw comfrey every day, and when she went back for a checkup a few weeks later, the doctor said her blood was perfect.

89 year-old comfrey user claims MD says he’s in perfect health. In 1991 Andrew Hughes, a comfrey user, published Comfrey, Nature’s Healing Herb and Health Food, which includes anecdotal stories of the benefits of ingesting comfrey. The 89-year old Hughes had been taking from 85 to 135 grams of comfrey in tablet form daily for 28 years, at the time of writing, and he says his regular check-ups revealed perfect health. Hughes first discovered the power of comfrey in 1956, and upon moving to Japan, became an advocate for it. His efforts led to a comfrey boom in Japan, the plant being widely used by Japanese farmers because it increased productivity enormously.

Australian man’s stock is legendary for its health. Foster Savage, who takes credit for introducing comfrey into Australia in 1954, fed it to his stock in great quantities (and ate quite a bit of it himself.) He found that milk production increased dramatically in his cows, with the bonus of thick cream. He also fed his pigs as much comfrey as they could eat and the quality of his meat became legendary. His butcher remarked that he had never seen pigs with such healthy livers.

According to Ingri Cassel, writing in the Idaho Observer in July 2002, comfrey is used as feed because it is considered the fastest builder of vegetable protein. In fact, the amount of vegetable protein obtained from an acre of comfrey can be nearly twenty times that obtained from soybeans.

Here are some more testimonials from articles gathered by Ingri Cassel, as reported in, “Comfrey: Tomorrow’s food, today’s medicine,” in the Idaho Observer. The first three are excerpted from “Blood Make You Faint? Comfrey Root Powder Heals All of Life’s Hard Knocks” by Judy Vallely, Health Freedom News, Vol. 6, #11, p. 40:

Comfrey quickly heals smashed nail on toe. “I’ll never forget when Joshua was two years old, he dropped a heavy toy on his toenail, splitting it right down the middle. I just kept sprinkling comfrey root powder over the mini-gusher of blood until only drips persisted within minutes of the accident. His sobs of pain subsided almost as quickly and one hour later, after a nap, he was proud of himself, hobbling around on his heel! The next day, at a pool party, the scab floated off exposing pink skin. His toenail grew in over the following two weeks.”

Comfrey root stops hemorrhage after childbirth and heals ulcer. “The root is a powerhouse of healing energy that, when applied to a wound, makes blood coagulate which stops bleeding. Taken as a tea sweetened with honey it stopped my internal hemorrhaging after the home-birth of our third child. Our birthing assistant Betsy was concerned about my heavy bleeding, but it decreased to a normal flow after two cups of the tea. Betsy’s ulcers never bothered her again after swallowing several pills made of the root. Years of medication didn’t measure up to the quickness of comfrey roots’ healing powers.”

Sore throat, cold symptoms, stomach cramps, headaches, gone. “Sinus problems and bad head colds respond quite favorably to several cups of hot comfrey root tea. Sore throats melt away after a few cups. It has even soothed my stomach and gas cramps that had been known to bend me over. Headaches and menstrual discomforts cease to be a bother after a cup or two.”

Broken arm healed in five days. The son of a registered nurse in Provo, Utah broke his arm, so she rushed him to the hospital. When the doctor x-rayed the arm, he told them the bone was clean broken, so clean that he would have to use a brace for a few days until knitting started, before applying a cast. He told them to return in five days. The arm was bare, so on arriving home, his mother put comfrey poultices and fomentations around the arm and gave him comfrey tea, comfrey green drink, comfrey tablets and capsules, and put comfrey into salads and steamed comfrey as a vegetable — in fact, she got comfrey into him every way she could think of. Five days later, when she took him back to the doctor to get the cast, the doctor took another X-ray. He said, “What have you done to this boy?” He proceeded to announce the bone was knit together without even a hairline crack. This story is excerpted from the article “Comfrey — Heaven’s Gift to Man” by Dr. John R. Christopher, M.H., The Herbalist, Volume 1, Number 5, 1976.

Woman with deteriorated vertebrae able to walk again. Another story from the same article is about a woman with one-and-a-half vertebrae that had deteriorated in her back, and the vertebrae below and above were so weak that fusing could not be done. “She could not sit up or walk, but just lay there waiting for the spine to continue deteriorating until she died. We told the lady that her friend could be helped if she would follow our instructions. The back was to be kept with fomentations and/or poultices of comfrey on it, and she was put onto the mucusless diet and lots of fresh raw juice and many cups of comfrey tea each day, slippery elm gruel and a nerve palliative tea combination. In six months, the one and one-half vertebrae grew back in the same form as before (the good Lord left plans and specifications) in the form of cartilage so the woman could sit and walk again. In another six months, the cartilage turned into bone and she had a perfect back from neck through tailbone with no more trouble. The physician took x-rays of the back with vertebrae gone and later again with them back in place, built like new by the body.”

If you spend any time at all around people who use herbs to promote healing, you have probably heard a few good comfrey stories directly from your friends.

Comfrey saves baby’s life. Here is a story about how comfrey saved the life of my friend’s baby. Her two-month old daughter became plugged up and had great difficulty breathing. Doctors treated it as a bad cold at first, but the condition persisted for nine months. Four different pediatricians prescribed antibiotics, a humidifier, and misting machine, but none could find a cause or cure. The last pediatrician said the girl was dying and the mother should get her affairs in order. That’s when my friend went to the proprietor of a local health food store, who suggested she try comfrey. Dried comfrey leaves were made into a tea and put into a bottle. After drinking a few swallows, a brownish-yellowish mucus started coming out of the girl’s mouth, and she sounded like she was choking. The mother started cleaning it out, pulling it out of her mouth and then her nose, until she had extracted a mound the size of two softballs. That solved the problem.

Should comfrey be included in the prepper’s medicine kit?

So, what’s a prepper with a vigorous stand of comfrey to do? Are the benefits greater than the risks, or not? Has science even proven the risks? Are the scientific trials applicable to humans using moderate amounts of comfrey as food and medicine? Or, is its ban merely a move to protect the power and pocketbooks of the pharmaceutical industry, which plies drugs known to damage health? Whom should we trust? You are going to have to decide. As with everything in our complex world, independent thinkers need to separate the pepper from the fly droppings.

Some modern advice on how to use comfrey

“PA’s are believed to have an accumulative effect in the body and may cause hepatic vein blockage and liver toxicity. It is said that the PA’s are only converted to toxic metabolites, in the body, by the liver enzymes. When comfrey is applied externally to the skin, as a cream, it is not considered to be a significant intake of PA’s, in view of low dermal absorption of the PA’s. When comfrey is dried, enzymes are released and much of the alkaloid is destroyed,” according to herbsarespecial.com.

The site also points out that: “From trials, in Minnesota U.S.A. in 1987, it was found that comfrey, harvested at different times in the growing season, can be of varying PA amounts. Roots were found to have the highest concentration of PA’s, generally with 10 times as much as young leaves. In one trial, in 1986, immature leaves contained 0.026% pyrrolizidine, on a dry weight basis. A subsequent harvest during the growing season, had no detectable PA’s in the leaf (the minimum detectable quantity was 5 ppm). The data indicated, harvest time was a critical factor in producing PA free comfrey, and that mature leaves have an even lower alkaloid content, than young leaves.”

The University of Maryland Medical Center says children, the elderly, pregnant or breastfeeding women should avoid using comfrey in any form. Same with alcoholics and those with liver disease or cancer.

The U of M Medical Center echoes the opinion that people can die from taking comfrey by mouth. They say to avoid applying it to broken skin, and that topical use should not last longer than 10 days.

Don’t mix comfrey with medications that are hard on your liver, i.e. acetaminophen, and avoid using it with other herbs “known” to cause liver problems, such as kava, skullcap, and valerian. Finally, only use comfrey with the supervision of your health care provider.

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