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Comfrey and Alkaloids: More Studies Needed
I sell live Comfrey roots, seeds, dried comfrey and oil.
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My comments are in brown. -Nancy

Comfrey Toxicity Tests Were Unrealistic

Inaccurate Reports, Poor Testing

"Comfrey is the victim of a bad press, inaccurate reports, and four true cases of toxicity which in themselves are not straightforward, but suggest overdosing on comfrey."

"When the toxicity tests were done in the late 70s, a chemical constituent called pyrrolizidine alkaloid was isolated, extracted from comfrey leaves & injected into baby rats at what many medical herbalists consider an 'unrealistic level'. In other words far more comfrey than a human would eat to get such a toxic level of PAs."

Good if Used in Moderation

"Also, a chemical in isolation will cause different reactions from a group of chemical constituents containing that one as well."

"Yes, the pyrrolizidine alkaloids (PAs) in comfrey do hurt your liver. Yes, you have to take lots of the herb in order to get veno-occlusive liver disease. So don't take lots of comfrey every day for weeks at a time; if you do believe that you need it, take it in small amounts."

"And know, too, that PAs are absorbed through the skin. That means that it's a really bad idea to use comfrey long-term for wounds."
(The above 5 paragraphs are from Henriettes Herbal, Henriette Kress,

Seek the advice of your physician, herbalist or health care specialist for more information about comfrey and you.

Not Enough Research on Alkaloids in Comfrey: No Long-Term Studies

1. No Long-Term Studies. Some Evidence in Lab Animals But What About People?

"There are no substantial, long-term follow-up data to assess whether exposure to PAs results in increased incidence of chronic liver disease or cancer in man. Available clinical and experimental data suggest that a single episode of PA toxicity and possibly also a long-term low level exposure may lead to cirrhosis of the liver."

"The International Agency for Research on Cancer (IARC) evaluated several PAs for carcinogenicity in 1976 and 1983. It was concluded that there was in experimental animals 'sufficient or limited evidence' for the carcinogenicity of monocrotaline, retrorsine, isatidine, lasiocarpine, petasitenine, senkirkine, and of extracts of the PA-containing plants Petasites japonicum, Tussilago farfara, Symphytum officinale, Senecio longilobus, Senecio numorensis, Farfugium japonicum and Senecio cannabifolius."
(The above 2 paragraphs are from the European Medicines Agency, October 25th 2012, Committee on Herbal Medicinal Products, en_GB/document_library/ Public_statement/2012/10/ WC500134311.pdf.)

Not Enough Research on Alkaloids in Comfrey: Limited Verification

2. Human Cases of Toxicity are Poorly Validated

"The available reports on human poisonings do not provide sufficient reliable information to be used as a basis for establishing a health-based guidance-value."
(European Food Safety Authority, Scientific Opinion on Pyrrolizidine Alkaloids in Food and Feed, 2011, en/search/doc/2406.pdf)

3. Only 2 Significant Comfrey Studies

"Despite all the rhetoric there are in fact only two full-scale toxicological studies on Comfrey. To quote other publications which merely interpret the findings of these two studies does not constitute additional evidence."
(GardenWeb, Comfrey- The Facts, 2004, Scientific research is referenced with citations. load/herbal/msg080635098259.html)

Treating All Comfrey Alike

True/Common and Russian Comfrey Treated as Same Plant

"Another problem with the studies which were done on comfrey is that the researchers often did not differentiate between the different species of comfrey. Russian comfrey (Symphytum x uplandicum) contains up to 5 times the amount of PAs as common comfrey (Symphytum officinale). However, in one study, the names S. x uplandicum and S. officinale were used interchangeably."
(Kerry's Herbals, comfrey_safety.shtml)

Moderation is Key in All Things

Too Much of A Good Thing

"The safety of Symphytum has been a contentious issue between scientists and the herb industry. It is true that the number of documented cases of Symphytum poisoning is low. Acute toxicity is low. A 47-year-old woman developed liver disease after drinking up to 10 cups of comfrey tea per day and consuming comfrey pills in addition, over a period of 1 year."
(Handbook of Natural Toxins: Food Poisoning, 1992.)

Another article said she took "comfrey pills by the handful".
(Quote is from 'Safety Issues Affecting Herbs: Pyrrolizidine Alkaloids' by Subhuti Dharmananda, Ph.D., Director, Institute for Traditional Medicine, Portland, Oregon,
I do not know what type of comfrey this woman was using. And I do not know what other herbs, medications, foods, etc she was consuming.

As In All Things, Do Not Go to Extremes

"If you want my straight up opinion on PAs. I donít use it too much internally anymore. Yeah, I know, itís a traditional food. And yeah, Iíve read Susun Weed ( But Iíve also read what Paul Bergner, Henriette Kress (, David Bunting and other have to say about it."
(Medicine Woman's Roots, bone-deep-beauty-notes-on-comfrey.html)

Be moderate. Use comfrey internally for a specific problem for a short period. External use is safer (or safe). Do research on the internet and in books for more information. Consult your physician and/or health care provider.

Use Comfrey Carefully

Herbalists vs Regulatory Agencies

"The debate on the toxicity of comfrey and coltsfoot for internal use pits traditional herbalists against regulatory agencies. The traditional herbalists argue that these plants have been widely used for centuries without any observed ill effects. Regulatory agencies point to evidence that pyrrolizidine-alkaloid-containing plants, and comfrey and coltsfoot in particular, have caused liver disease in humans."

"The evidence suggests that both plants should be used with cautionó especially for long term use, for pregnant and lactating women, and for children. It is not easy to identify a toxic dose of pyrrolizidine alkaloids."

(Paul Bergner, Medical Herbalism: Materia Medica and Pharmacy,,_Coltsfoot,_and _Pyrrolizidine_Alkaloids.htm)

Use comfrey wisely.

Comfrey and Healing
Comfrey Soap
Comfrey: Animals & Health
Comfrey Safety: Overview
Comfrey Safety: Processing
Comfrey Safety: Research
Comfrey: Need Studies

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