Comfrey: toxicity.

Date: Fri, 22 Jul 1994 15:59:16 -0400
Sender: "Medicinal and Aromatic Plants discussion list <HERB.TREARN.BITNET>
From: "Mark D. Gold" <GOLD.ILP.MIT.EDU>
Subject: Re: Uses of comfrey?


I just posted the attached email to USENET. Since there has been quite a bit of fear related to the use of comfrey (some justified, but some caused by FDA fear-mongering), I thought I'd post my $0.02.


The concern that researchers have about comfrey is that it contains pyrrolizidine alkaloids (PA). PA has been linked to causing hepatic veno-occlusive disease of the liver. However, the PA in comfrey is less toxic than in other plants such as senecios. [See British Medical Journal, Volume 295, 18 July 1987, pp. 183.] So, it is extremely rare that comfrey has been linked to veno-occlusive disease (a handful of cases worldwide, I think). In most of these cases, the person was taking comfrey for a long period of time and/or using extremely large doses.

So, many herbalists still use comfrey internally in relatively small doses for short durations. Sometimes it is used with liver-protecting herbs such as Silymarin. Even though short-term use of comfrey almost never causes any problems (and is extremely useful), some people are still a little nervous about using it. To solve that problem, there is at least one comfrey extract that I know of that have the PA removed (from Herb Pharm). So, if there is a good reason to use comfrey, it can be used, one way or another.

I've never seen any studies that show comfrey causes cancer. I remember reading a study that shows PA, by itself, in fairly large doses can cause tumors in rats. Anyone have more information on PA or comfrey and cancer?


I read somewhere that in the U.S., 80 people die each year from causes linked to taking (not overdosing on) aspirin. There are thousands of other cases of people dying from taking prescription and non-prescription pharmaceuticals. For example, over 10,000 deaths in the U.S. each years are linked to NSAIDs [see Journal of Musculoskeletal Medicine (Feb, 1991 pg. 21 to 29--vol 8(2)]. I have never seen documented more than a few cases worldwide over the past twenty years of people dying from taking comfrey.

I do not believe that everybody should run right out and start drinking comfrey tea regularly. However, I do not think we should fear its prudent use because of a handful of problems worldwide. People still take pharmaceutical despite the widespread serious health consequences and death cause by them. I have known quite a few people that have used it without any problems both internally (mostly in herbal formulas for asthma) and externally.

If we try to live up to the standard of perfection -- "herbs never cause any problems anywhere in the world or else they should be banned" -- rather than trying to obtain an excellant risk/benefit ratio (as is _supposedly_ done with pharmaceuticals), we open ourselves up to the banning of many herbs.

Chaparral is a another example of a herb that can be extremely useful. Not too long ago, the head of the FDA held up chaparral before the U.S. Congress as an example of an herb that can cause death. The link between chapperal and a handful of problems worldwide over the last 20 years is still being debated. Yet, the FDA used this fear-mongering to begin pressuring chaparral off the shelves.

Well, maybe my opinions are not that of the typical user and promoter of herbalism, but that never stopped me from standing up for my beliefs.

- Mark