George Meinig, DDS: Sister’s Distress Over Remedy Is Backed by Research and Study of Comfrey Usage

Dear Dr. Meinig:

Yesterday my sister chewed me out something fierce when I offered her some comfrey tea to ease her stomach distress. She said it could cause serious illness, but she did not ·remember where she had heard about it. Inasmuch as the English have used it as a vegetable and a tea for a long time, I find it hard to believe. – M.J.

 

Dear M.J.:

If your sister is a longtime reader of this column, she could have learned it from an article of mine about the problems of comfrey that appeared in the OVN on March 27, 1985.

Interestingly enough, the F.D.A. has recently been analyzing comfrey products that are on the market as food supplements and for tea. The harmful substances comfrey contains are pyrrolizidine alkaloids (PAs) which include symphetine, lycopsamine, symglandine and echimidine. The presence of these substances in this so-called health product has been a worry for some time as they are also present in other herbs such as coltsfoot and borage.

ln March of 1989, Dr. P. M. Ridker and Dr. W. V. McDermott reported three cases of liver vein closure that occurred after the use of comfrey tea. An additional case of vein closure occurred in a newborn infant whose mother drank comfrey tea.

The doctors were apparently unaware of the study I reported in my previous article that was conducted under the auspices of the cancer division of the University of Tokyo, the Gifu University School of Medicine, and the Department of Pharmaceutical Sciences of the Gakuen University. They found liver cancers in all experimental groups of rats and a small number developed urinary bladder tumors.

Over 200 rats were divided into seven different groups and fed comfrey leaf or roots in varying amounts. All groups developed cancers, and the rate at which they evolved ran from 86.3 percent to 4 percent, depending on the amount of comfrey eaten. This represented a one to 33 percent concentration of the herb in the diet. Strangely, the highest number proved to be in rats on 8 percent of the comfrey root, indicating that roots were more virulent than the leaves. In the control group, 266 rats not eating comfrey were free from cancer.

Subsequent studies by the Toxicology Unit of the M.R.C. Laboratories in England show the highest alkaloid levels to be in small young leaves grown early in the season. Leaves picked the first two weeks of the growing season contained 0.115 percent alkaloids, while in mid-September the level fell to 0.019 percent.

The National Products Chemistry Division of the U.S. Department of Agriculture at Berkeley found that 1½ teaspoonfuls (8.7 grams) of chopped root boiled in 250 ml. (8+ ounces) of water contained 8.5 mg. of alkaloid (33 percent of the sample). Although considerable data is available as to the toxicity of pyrrolizidine alkaloids on animals, very little has been carried out on humans.

The most reliable report concerns a study on 7,200 people who weren’t on comfrey, but had eaten wheat flour contaminated by the same toxic substance. Within two years, 23 percent suffered severe liver impairment. Individuals who drink comfrey tea should expect the dose to be four to 13 times as great as the wheat flour group.

From time to time I have warned readers that our knowledge about all the different ingredients contained in herbs is quite deficient. Consequently, they should only be consumed occasionally. To use them for a short period to treat a medical problem is one thing, but people then find herbs intriguing and continue their use daily in excess.

The reason comfrey is found to be helpful is its allantoin and high mucilage content. Several other plants such as marshmallow root and aloe vera are high in mucilage and can be reasonable substitutes for comfrey.

The Canadian government has banned the use of comfrey, and Germany and Australia are finalizing regulations of the use of this herb.