Comfrey hepatotoxicity.

Botanical name: 

Date: Thu, 14 Sep 1995 01:39:34 EDT
From: Rene Burrough <100735.543.COMPUSERVE.COM>

Comfrey is the victim of a bad press, inaccurate reports, and four true cases of toxicity which in themselves are not straight forward, but suggest overdosing on comfrey. Governments in the UK & Australia have restricted the uses of comfrey root or banned the plant respectively.

The problem is two fold: firstly there are two "comfreys" (there are many more. I have three in my garden ... --Henriette) and reference to them is often casual. Regular, common, medicinal comfrey is Symphytum officinale. Russian comfrey, the great compost heap maker, is Symphytum X uplandicum. Medical herbalists in the UK, from whose written reports I am extrapolating, point out that Russian comfrey was probably the herb used in the toxicity trials yet regular comfrey is also restricted or banned.

Secondly,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>. Also baby rats are smaller than humans; they do not have the same metabolism as humans; and an isolated chemical injected outside the rat's stomach wall is not the same as a human eating leaves with many chemical constituents and digesting them normally. A chemical in isolation will cause different reactions from a group of chemical constituents containing that one as well.

To digress, but to explain, I hope. Aspirin is a synthesized chemical, acetylsalicylic acid, based on a real life plant constituent found in meadowsweet & willow. Aspirin can cause ulcerations of the stomach lining; meadowsweet has a soothing, gummy constituent called mucilage which lines the stomach, preventing erosion of the stomach wall but allowing the anti inflammatory properties of the salicylates of the herb to be utilized. OK?

So -- the bad guys in <comfrey>, the <PAs> were isolated & did bad things.But that too must be qualified.

The early research, late 70s, concluded that these <PAs> do indeed cause liver damage in humans. Medical herbalists would point out that Pyrrolizidine alkaloids can cause obstructions of the veins in the human liver, known as hepatic veno-occlusion, but <were not shown to cause liver cell adnormalities> and that the level of alkaloids in comfrey was too low to <cause specific damage to liver ciruclation> in any case.

And finally, is comfrey carcinogenic? The carcinogenic alkaloid has been identified as symphytine which apparently is about 5% of the total alkaloids in comfrey.

The original, often cited report was written by Culver et al in 1980. There have been many criticisms since of the research itself; how the scientific testing was conducted, which comfrey was really used, etc. What I found most interesting was the tumors in all but three of the rats were benign -- out of three groups of 19-28 rats and 3 groups of 15-24 rats. <And the three malignant tumors were of low malignancy>. There were clear cut cases of liver damage. That's in rats.

There are four cases involving humans which due implicate comfrey. One involved a woman who was finally diagnosed as having veno-occlusive disease & did consume a quart of herbal tea/per day that contained comfrey. A second case involved a boy with Crohns disease who was treated with conventional medicine for some time before going over to comfrey root & acupuncture. The long running malnutrition may have weaken the liver predisposing it to the venal obstruction problem. Comfrey root was blamed. The drugs were not considered as possibilities. The third case involves a woman who overdosed: 10 cups of comfrey tea a day & handsful of comfrey pills. After 9 years, she had serious liver problems. The fourth case became a fatality. A vegetarian, given to specific food binges for weeks, took an unknown amount of comfrey for flu like symptoms possibly over a period of four months. The particulars of his case are blurred. All cases involve comfrey; in at least three, there are suggestions of overdosage or abuse of the plant. WHICH plant, I don't know.

There are also disagreements about the efficacy & safety of leaves vs root. Some studies show the leaf to be almost alkaloid free -- thus safe. The UK finally restricted the internal use of comfrey root...saying that there are still too many unanswered questions. Most medical herbalists I know will politely to vigorously disagree, but the law restricts the root. At least externally the root's OK here & the leaves can still be used as tea or poultice.

I'm sorry this is so long, but bear with me one more paragraph, please. I must credit Penelope Ode, MNIMH, former Editor, writing in Herbs, the British Herb Society magazine & Margaret Whitelegg, MNIMH, whose paper for the National Institute of Medical herbalists to the UK government in <Defence of Comfrey> was later published in the European Journal of Herbal Medicine. Both were published in 1993.I cannot do justice to their articles so briefly, but I do hope I have fairly sumarized their writings. Any misstatements, confusion of explanations here are mine.

Rene Burrough

From: Rene Burrough <100735.543.COMPUSERVE.COM>

> How can I tell which type of comfrey I have growing in my garden? The plant was a start from some friends who don't know it as anything but plain old comfrey.


I'm kinda sorry you asked that question, cause I ain't no botanist. However, I have Lawrence Hills' book on Comfrey. He is the closest UK equivalent to the Rodales I that I know of. And I have my Mother's old copy of J I & Robert Rodale's Encyclopedia of Organic Gardening. So being basically bi-lingual (an American living in the UK for many years now), I shall try to work out what these two comfreys look like.

Russian Comfrey, Symphytum X uplandicum, is described as a <perennial fodder crop> on both sides of the pond. In the States, it's also known as Quaker comfrey or Prickly comfrey -- which may actually be another comfrey [S. asperum ] & truly a fodder crop only. Comfrey has a deep, powerful root system - so it's good for breaking down heavy clay & will happily grow on poor soil. The Rodales do not not mention the medical comfrey, Symphytum officinale, at all.

Lawrence Hills did extensive research into the breeding, strains, & uses of Russian comfrey. But he only included one line drawing. That shows Russian Comfrey as a triangular shaped bush; very heavily leafed at ground level; too many really...serious middle age spread!!! Then flower stems also heavy with leaves & all narrowing into a fat point. Sort of overweight compared to the only photo I've got of the entire Common Comfrey plant. [Most of the herbals concentrate on isolated flower stalks.] The Common Comfrey is narrow at the base; you can actually SEE the thick stalks at ground level before the long leaves & flower stems. It's vertical growth. A very trim plant - compared to the chunky Russian drawing .

The flowers of the Common Comfrey seem to grow out of the leaf axil [angle between thick stem stalk & leaf stem] on a short stem. The flowers on the Russian comfrey may be fatter - or maybe there are more of them - and on longer stems.

For a proper botanical description: Common Comfrey, Symphytum officinale, is also a member of the Borage family. A perennial, 12-48"(30-120cm) tall. It has large 12" or 30cm long leaves in a lanceolate shape. Rough to the touch, covered with short sticky hairs. Thick stems. Upright plant. Flowers are mauve or white, borne in cymes [broad inverted cone-shaped flower cluster in which the central flowers open first] on forked stalks above the top leaf, each stalk supporting short one sided racemes of pedicillate [short stalk holding flower] bell-shaped flowers. The root is thick, quite short & very branched from the crown. Its greyish with a white-cream core. Habitat on moist banks, fields borders, ditches & pond sides.

The only real difference I can see in the various herbals & gardening books I've got -- and of course nothing was shot for comparison -- is that the flowers grow more closely to the main stems on the Common Comfrey whereas they're a bit more flopped out - away from the stems on the Russian Comfrey. And if you don't have both in your garden, you may never know.

If it makes you feel any better: the type I have is allegedly Russian comfrey -- the flower description does match -- although it's much taller. Russian comfrey, according to the Lawrence Hills research folk, doesn't spread the way common comfrey can. Well, my comfrey is very promiscuous and couldn't care less where it grows.

Rene Burrough

From: Rene Burrough <100735.543.COMPUSERVE.COM>

> Could anyone tell me if there is any significant difference between comfrey and Russian comfrey in terms of medicinal and culinary uses?

I have always regarded regular comfrey as the medical plant & Russian comfrey as the compost maker & fodder plant. As medical herbalism is my avocation and not vocation, I call only repeat what I have learned in courses and what my herbals say. Symphytum officinale is the medical herb.

Russian comfrey is high in potash & the leaves can be used in potato trenches before planting the chitted tubers; as a mulch for tomatoes -- a high potash feeder -- especially, or made into a liquid feed by soaking the comfrey leaves in a vat of water for a longish period. The smell is a little strong, but it a good natural fertilizer.

As for eating comfrey, there are those who would question the wisdom of that. It can certainly be prepared as spinach. But I wouldn't abuse the herb by having a comfrey leaf only diet. I think any unbalanced diet in unhealthy.

From: Henriette Kress <HeK.HETTA.PP.FI>
Subject: Restriction on use of Symphytum in your countries?

Hello all,

This just went out on the phytopharmacognosy list:
> A friend with a herbal farm/firm/herbshop would like to use Symphytum officinalis in her products for external use.
> Before Finnish authorities permit even that they require her to test each batch of plant material for pyrrolizidine alkaloid content.
> She attempted this some years ago, but the testing lab was unable to find a source for pure pyrrolizidine alkaloid, so no test - no permission to use Symphytum.
> Could you help me find a source for pyrrolizidine for her?

In addition, she fears that, even if she gets the pyrrolizidine, and makes the tests, the Finnish authorities will find another 'but' to stop her from using Symphytum in any products at all.

So we (= Finns, being all in this together) need to convince the Finnish authorities that the external use of Comfrey isn't all that dangerous.

One of the ways to accomplish this is to prove that it is widely used in Canada? Germany? France? U.S.A? U.K.? Anywhere else? including, if internal use is banned, why external use isn't; and if internal use isn't banned, why not.

Please help.

The same goes for Petasites hybridus and Borago officinalis... but let's start on Symphytum.

Thanking you all in advance,

From: Colette Gardiner <coletteg.EFN.ORG>

I believe that there have been several research papers showing skin absorption of pyrolizidine alkaloids to be minimal if not completely non existent. Try "Pyrrolizidine alkaloids from Symphytum officinale L. and their percutaneous absorbtion in rats", J. Brauchli et al., Experientia, Vol. 38, 1982 pp. 1085-1087 also try "Pyrrolizidine alkaloids in S. officinale and their dermal absorption in rats". same author Experientia, 1981 pp 667. If you think these may be helpful and you can't find them let me know. There may be something more recent as well.

Colette Gardiner