Slippery Elm – An American Enigma

Early in his career in the mid 1960s, Chicago Cubs Hall-of-Fame pitcher, Gaylord Perry, started down a path that eventually earned him infamy for a famous pitch—the spit ball. He is said to have tried a little of everything to confound the batter and make the pitch turn, roll, bounce, and jump. Mud, K-Y jelly, Vaseline, sweat, and Wrigley's Spearmint Gum, in honor of the Cub's owner Mr. Wrigley, are just a few of the substances he tried—before major league baseball outlawed the spit ball. Slippery elm tablets or little slivers of the slippery elm bark that he harvested on his father's farm are said to have been his favorite. Still available at corner drugstores and health food stores, slippery elm is an often-neglected herb with more uses than many of us are aware. In the United States, most major herbs, backed by numerous scientific studies and clinical trials, such as ginkgo, saw palmetto, and Echinacea are relegated to the realm of dietary supplements. Manufacturers cannot make medicinal claims for these products. Only approved prescription and non-prescription drugs and medical devices can make therapeutic claims. Lacking any clinical literature and backed by scant scientific studies, slippery elm bark is an enigma in the current market. While slippery elm is widely available in dietary supplement products, it is also an approved drug! Currently it allowed to be sold as an over-the-counter (OTC) or nonprescription drug for demulcent purposes for the oral cavity (soothing to irritated membranes, such as a minor sore throat).

What is Slippery Elm?

Botanists deem slippery elm Ulmus rubra Muhl., named by the Pennsylvania botanist, Henry Ludwig Muhlenberg (1756-1817) in a 1793 publication. The eminent French botanist who spent ten years in America and authored the first floristic work of North America, Andre Michaux (1746-1802) named the tree Ulmus fulva. However, the name Ulmus rubra was published first, therefore it has priority. Unfortunately, many herb books still use the long obsolete name Ulmus fulva. Ulmus is the classical name for elms. The species name “rubra” meaning red, refers to the rust color of the tree's buds before the leaves appear in spring. Our common name “elm” is the ancient name from Anglo-Saxon, Celtic, Gothic, and Teutonic dialects, remaining unchanged in modern English. Knowing the current scientific name for a plant can be extremely helpful if you are looking for information or for a tree properly labeled in a botanical garden. I happened to be in the Boston area for the weekend and needed a picture of a slippery elm tree. I journeyed over to Harvard University’s Arnold Arboretum in Jamaica Plains. There I spent an afternoon sauntering through the splendid elm grove searching for a tree tagged Ulmus fulva, the name I had in my head as the “correct" name for slippery elm. To my dismay, no such tree was to be found. Then, I looked the tree up in a botanical manual, only to discover the tree labeled Ulmus rubra I had passed several times was, indeed, the Ulmus fulva for which I had searched!

Slippery elm has a number of distinctive features that make it easy to distinguish from other eastern North American elms. The leaves look very much like those of American elm (Ulmus americana). However the leaves of slippery elm are sandpapery on the upper surface, while those of American elm are smooth to the touch. Slippery elm’s silky wafer–like fruits, unlike other native elm species are smooth-edged and hairless along the edges. Other eastern North American elms have a hairy fringe on the fruits margins. Slippery elm occurs from dry upland soils to moist limey stream banks from Maine through the St. Lawrence Valley to the Dakotas, south to Texas, eastward to Florida. Like American elm, slippery elm is also attacked and killed by Dutch elm disease (from the fungus Ceratocystis ulmi).

In the last century, so much bark was harvested, that slippery elm became threatened. In 1837, the Legislature of Massachusetts initiated a study of the woody plants of the state by George B. Emerson, a distinguished Boston schoolmaster. The result was a classic American tree book — A Report of the Trees and Shrubs Growing Naturally in Massachusetts (1846). In the second edition, published in 1875, Emerson decries the fact that the tree had become rare in eastern Massachusetts due to over-harvest of the bark:

“In many places I have found it dead or dying, from having been stripped of its bark. . .It is much to be regretted that the slippery elm has become so rare. The inner bark is one of the best applications know for affections of the throat and lungs. Flour prepared from the bark by drying perfectly and grinding, and mixed with milk, like arrow-root, is a wholesome and nutritious food for infants and invalids.”

Importance in History

It is the inner barkof the tree that is used for herb products. The bark is tawny or buff white in color, and highly mucilaginous or “slippery.” It has a faint but distinctive, sweet, fenugreek-like scent, and a bland, mucilaginous taste. Slippery elm emerged as an important domestic remedy, and in some cases, as a survival food in colonial America. The first work on American medicinal plants, J. Schoepf's Materia Medica Americana (1787) listed it as “salve bark.” Nineteenth century physicians and herbalists recommended slippery elm for a plethora of ills. Pneumonia, consumption, pleurisy, and other lung afflictions were treated with slippery elm tea. Giving a large dose of the tea—literally sliding the parasite out of the digestive tract—expelled tapeworms. Skin ulcers, abscesses, inflammations, fresh burns, chilblains, boils, carbuncles, herpetic and syphilitic eruptions and even leprosy were treated with the bark poultice. The poultice had to be kept continually moist as it tended to dry out and harden, making it stiff and uncomfortable. Early nineteenth century physicians made a broth from the bark as a food for sick infants and invalids when other food could not be retained in the stomach. One book suggests that slippery elm bark made a good “formula” for weaning infants. A tablespoonful of the bark powder, cooked in a pint of milk, “affords a nourishing diet for infants weaned from the breast, preventing the bowel complains to which they are subject, and rendering them fat and healthy”, wrote H.W. Felter and J. U. Lloyd in King’s American Dispensatory (1906).

In colonial America, the powdered, mucilaginous bark was also used as a pudding base. Slippery elm bark proved important as both a food and drug in early American conflicts. In the field, surgeons of the American Revolutionary Army used a poultice of slippery elm’s inner bark as a primary treatment for gun shot wounds. In the American Revolution, one soldier, separated from his company, survived in the wilderness for ten days on the barks of slippery elm and sassafras. During a snowy winter in the War of 1812, The US Army troops on the Canadian frontier fed their horses the inner bark of slippery elm when hay could not be found.

The use of the bark was learned from Native American groups. Midwestern Indians groups used the fresh inner bark to make a soothing laxative. The Omaha cooked buffalo fat with the inner bark to render out tallow. It was said to be useful as a preservative to prevent bear's fat, butter, and lard from becoming rancid. An article on this subject appeared in a pharmacy journal in 1852. In the experiment, the author, Dr. C. W. Wright wrote that when fatty substances are heated for several minutes with one part slippery elm bark to 128 parts of the fat, that the fat could then be easily separated by staining, while preventing the fat from going rancid.

Slippery elm throat lozenges made by the Henry Thayer Company have kept this herb on drugstore shelves for over a century. Henry Thayer (1823–1902) was the son of a doctor from Milford, Massachusetts, whose ancestry dates to the Massachusetts Bay Colony. Dr. Thayer opened a retail apothecary in 1842, and by 1847 was manufacturing pharmaceutical preparations. During the mid-nineteenth century, Henry Thayer & Co., then of Cambridgeport, Massachusetts was best known as a manufacturer of fluidextracts for physicians. Later it began to produce various preparations for the consumer market. Thayer's slippery elm lozenges first appeared sometime in the late 1800s. Slippery elm lozenges are still manufactured today by Thayer's Natural Remedies of Westport, Connecticut as well as other manufacturers.

I have found slippery elm lozenges to be helpful in soothing sore throats and tickling coughs. Although commercially prepared slippery elm lozenges are readily available, sometimes I prefer to make my own. Simply make a thick paste with powdered slippery elm bark and honey. Roll into marble-sized balls, dusting the exterior of each lozenge with a coat of dry Slippery elm powder or confectionery sugar. Store in the freezer in a closed container until needed.

Modern Use

In these days when so much focus is placed on European herbal traditions and their scientific basis, it is ironic that one of the few herbs actually approved as a nonprescription drug in the United States is rarely used in Europe. It is not even mentioned in the German regulatory texts, although is mentioned in many British herbal works. Slippery elm’s demulcent action (soothing to irritated membranes) is due to its content of carbohydrate constituents, especially mucilage. It also contains a number of sugar-like compounds. Slippery elm powder is widely available wherever herbs are sold. Traditionally it has been used in a tea or lozenges to help soothe a sore throat. It was also used to help relieve coughs. Once an ingredient in coughs syrups it probably served more as a thickener for the syrup than to actually help suppress coughs. It is no longer approved as an antitussive ingredient in cough syrups. The bark is rarely seen in the market in whole form. In England it is not sold in whole form because slivers of the bark were once used as a mechanical abortifacient. When water is added to a sliver of the whole bark, it becomes self-lubricating. Prior to the legalization of abortion in the United States, there were instances where desperate women, in an attempt to abort a fetus would insert a sliver of slippery elm bark into the cervix to mechanically induce an abortion. This practice sometimes resulted in the user’s death due to hemorrhaging or infection. Slippery elm is one herbal remedy that has survived the test of time. Traditions tend to be cyclic in nature. Slippery elm is as useful today as it was 100 years ago.

References

1. Emerson, George B. A Report on the Trees and Shrubs Growing Naturally in the Forests of Massachusetts. 2 vols. 2nd ed., Boston: Little, Brown and Company, 1875.
2. Felter, Harvey Wickes and John Uri Lloyd. King’s American Dispensatory. 2 Vols. 18th ed., 3rd rev., 1906; reprint ed., Portland, Oregon: Eclectic Medical Publications, 1983.
3. Foster, S. 101 Medicinal Herbs — An Illustrated Guide. Loveland, Colorado: Interweave Press, 1998.
4. Foster, S. and V. Tyler. Tyler’s Honest Herbal. 4th ed. Binghamton, New York: Haworth Press, 1999.
5. Barnes, J., L.A. Anderson, and J. D. Phillipson. Herbal Medicines: A Guide for Health-Care Professionals. 3rd ed. London: The Pharmaceutical Press, 2007.
6. Tyler, V. and S. Foster. “Herbs and Phytomedicinal Products.” In Handbook of Nonprescription Drugs, 11th ed. Washington, D.C.: American Pharmaceutical Association, 1996.