A Bark with Benefits: What Is Slippery Elm?
The aptly named slippery elm tree, or Ulmus rubra, is a deciduous tree that is native to most of North America, and it was designated as a specific species in 1793 by Gotthilf Muhlenberg, a German American clergyman and botanist from Pennsylvania.1 Slippery elm trees can grow to a height of 65 feet and may have a diameter as large as 20 inches.2 The tree's distinctive feature is its slimy inner bark. It is this mucilaginous product that functions as a demulcent, or anti-inflammatory agent, and it may also serve as a nutritional substitute.1
Slippery elm has a laudable history in the United States, beginning with the early settlers. During the American Revolution, soldiers found its paste useful as a salve for healing wounds. The bark and its resultant mucilage not only contain anti-inflammatory agents, but also contain nutrients such as vitamin E and bioflavonoids.3 According to several sources, slippery elm played a role in saving soldiers from starvation during the brutal winter at Valley Forge.3 It was recommended in King's American dispensatory and was also included in the United States Pharmacopeia from 1820 to 1960.4
The medicinal uses of U rubra have been documented for hundreds of years. The mucilage of this tree bark is a complex polysaccharide that becomes a gel-like substance when mixed with water. Native Americans noted using formulations of the mucilage for wound healing, skin conditions, cough control, and sore throats.5 As pioneers moved into the frontier, folk medicine and Native American healing methods gradually merged, and slippery elm continues to be used today for a variety of conditions. One unique use for slippery elm was the chewing of slippery elm tablets by baseball pitchers to enhance saliva production for the famous spitball, a practice that was banned in 1920.6
Slippery elm's most popular use is for the treatment of inflammatory conditions of the gastrointestinal tract. The mechanism of action in the upper stomach and esophagus appears to be reflux stimulation of the nerve endings in the lining, which causes increased mucous secretion.7 This increases the protective coating, shielding the stomach and small intestine from excess acidity.8
In one study, slippery elm was found to elicit a similar response in patients with the inflammatory bowel disease ulcerative colitis, when compared with 5-aminosalicylic acid.9 Researchers examined the anti-inflammatory effect of slippery elm on colonic cells biopsied from 45 patients with active ulcerative colitis. Findings revealed a nearly equal dose-dependent response in both slippery elm and 5-aminosalicylic acid.9
Slippery elm has also been used successfully for the management of irritable bowel syndrome (IBS). Taken orally as a dry powder, the water-absorbing capacity of slippery elm draws water into dry stool in the colon and adds bulk to loose and watery stools.10