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


Background


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

Science 


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

Safety, interactions


In addition to allergic reactions, which are always possible, slippery elm can also slow and/or inhibit absorption of other medications and should therefore be taken 2 hours before or after other medications.11 Slippery elm is not recommended for use in infants or small children. There are conflicting data regarding the use of slippery elm during pregnancy, but in the most current information on the oral use of slippery elm, it is considered safe for use in pregnancy. However, folk medicine resources and anecdotal sources describe miscarriages in women inserting small strips of the bark into the cervical os, as the bark absorbed moisture and expanded.12 The US Food and Drug Administration has granted slippery elm a status of generally regarded as safe.13

How supplied, dose, cost 


Slippery elm is available in a variety of forms. Tablets, powder-filled capsules, lozenges, ground bark for teas, and poultices are found in health food stores. Dose depends, to a large extent, on the intended use. However, for the common capsule formulation, 400 to 500 mg 3 to 4 times daily for up to 8 weeks is considered minimal.11 Capsules should be taken with a full glass of water. For conditions of a chronic nature, such as ulcerative colitis, long-term use will be necessary. 


Summary


Slippery elm appears to be a benign supplement with adequate research to support its use for many gastrointestinal complaints. Although its use alone may not be sufficient for serious conditions such as ulcerative colitis, its lack of drug interactions makes it a very attractive add-on therapy when additional symptom management is needed. 

Sherril Sego, FNP-C, DNP, is an independent consultant in Kansas City, Mo. 

References


  1. Jellin JM, Gregory PJ, Batz F, Bonakdar R, eds. Natural Medicines Comprehensive Database. http://naturaldata base.therapeuticresearch.com/home.aspx?cs=&s=ND. 

  2. Cooley JH, Van Sambeek JW. Slippery Elm. http://www.na.fs.fed.us/spfo/pubs/silvics_manual/volume_2/ulmus/rubra.htm. 

  3. Hanrahan C, Frey R. Slippery Elm. In: Longe JL, ed. The Gale Encyclopedia of Alternative Medicine. 2nd ed. Farmington Hills, MI: Thomson Gale; 2005. http://www.encyclopedia.com/doc/1G2-3435100729.html. 

  4. Anderson MK. Plant Guide: Slippery Elm. US Department of Agriculture Natural Resources Conservation Services. http://www.plants.usda.gov/plantguide/pdf/cs_ulru.pdf. Updated May 30, 2006. 

  5. Watts CR, Rousseau B. Slippery elm, its biochemistry, and use as a complementary and alternative treatment for laryngeal irritation. J Invest Biochem. 2012;1(1):17-23. 

  6. Spitball. Baseball Reference website. http://www.baseball-
reference.com/bullpen/Spitball. Updated November 28, 2015. 

  7. Blumenthal M, Busse WR, Goldberg A, et al., eds. The Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical Council;1998:167.

  8. Ehrlich SD, ed. Slippery elm. University of Maryland Medical Center website. http://www.umm.edu/altmed/articles/slippery-elm-000274.htm. Updated July 6, 2014. 

  9. Langmead L, Dawson C, Hawkins C, et al. Antioxidant effects of herbal therapies used by patients with inflammatory bowel disease: an in vitro study. Aliment Pharmacol Ther. 2002;16(2):197-205. 

  10. Hawrelak JA, Myers SP. Effects of two natural medicine formulations on irritable bowel syndrome symptoms: a pilot study. J Altern Complement Med. 2010;16(10):1065-1071.

  11. Skidmore-Roth L. Mosby’s Handbook of Herbs & Natural Supplements. 2nd ed. St. Louis, MO: Mosby Elsevier; 2005.

  12. Ehrlich SD, ed. Slippery elm. Penn State Hershey Milton S. Hershey Medical Center website. http://pennstatehershey.adam.com/content.aspx?productId=107&pid=33&gid=000274. July 6, 2014. 

  13. Das S, Shillington L, Hammett T. Fact sheet no. 17: Slippery elm. http://www2.ca.uky.edu/forestryextension/PDF/slipperyelmbark.pdf. January 2001.