Indian Elm, red elm, gray elm
Slippery elm is a tree native to North America. The bark of the tree is used as herbal medicine to treat gastrointestinal disorders, sore throat, cough, and skin ulcers. Slippery elm is thought to have antioxidant and anti-inflammatory properties. The primary constituent mucilage has demulcent effects. A small clinical trial showed that a formulation containing slippery elm improved the bowel habits and symptoms of constipation-predominant irritable bowel syndrome (IBS) (1).
Slippery elm is one of the components in Essiac, an herbal formula commonly used as an alternative cancer treatment. However, there is no evidence of antitumor effects in humans.
Adverse reactions or drug interactions have not been reported following use of slippery elm.
- Cancer treatment
- Peptic ulcers
- Skin abscesses
- Skin ulcers
- Sore throat
- Carbohydrates: Mucilage (hexose, pentose, methylpentose), galactose, glucose, galacturonic acid
- Phytosterols: Beta-sitosterol, citrostandienol, dolichol
- Fatty acids: Oleic and palmitic acid
- Other: Tannin, calcium oxalate, cholesterol
Mechanism of Action
Mucilage is responsible for the demulcent, emollient, and antitussive properties. Insoluble polysaccharides in mucilage (hexose, pentose, methylpentose) form a viscous material following oral administration or when prepared for topical use. Fiber content is thought to reduce gastrointestinal transit time, act as a bulk forming laxative, and adsorb toxins. Mucosal biopsies from patients with active ulcerative colitis incubated with slippery elm showed a dose-dependent reduction in oxygen free radicals (4). Another in vitro study also showed antioxidant scavenging activity (5). The tannin component can act as an astringent (2). Fatty acid esters such as oleic and palmitic acid are thought to be responsible for antitumor activity (3), but the specific mechanism remain unclear.
Theoretically, slippery elm may slow the absorption of concomitantly administered oral medications (6).
Literature Summary and Critique
Hawrelak JA, et al. Effects of two natural medicine formulations on irritable bowel syndrome symptoms: a pilot study. J Altern Complement Med. 2010 Oct;16(10):1065-71.
This two arm, open label, uncontrolled pilot study enrolled 31 patients who fulfilled the Rome II criteria for irritable bowel syndrome (IBS). The patients were classified as either having diarrhea-prominent or alternating bowel habit IBS (n=21), or constipation predominant IBS (n=10). A formula (DA-IBS) containing dried, powdered bilberry fruit, slippery elm bark, agrimony, and cinnamon was given to the patients with diarrhea-prominent or alternating bowel habit IBS. Patients with constipation predominant IBS were given a formula (C-IBS) containing dried, powdered slippery elm bark, lactulose, oat bran, and licorice root. The group receiving DA-IBS experienced a small, but significant increase in bowel movement frequency (p=0.027). Subjects in this group also experienced reductions in straining (p=0.004), abdominal pain (p=0.006), bloating (p<0.0001), flatulence (p=0.0001), and global IBS symptoms (p=0.002). Subjects who received C-IBS experienced an improvement in stool consistency (p<0.0001) and a 20% improvement in bowel movement frequency (p=0.016), as well as significant reductions in straining (p<0.0001), abdominal pain (p=0.032), bloating (p=0.034) and global IBS symptom severity (p=0.0005). The authors concluded that the DA-IBS formula mostly improved IBS symptoms in patients with diarrhea-prominent or alternative bowel habit IBS, but the C-IBS formula improved both bowel habits and IBS symptoms in patients with constipation-predominant IBS. They recommend that the C-IBS formula be further investigated as a potentially useful therapeutic formula for IBS. However, it is unclear if slippery elm alone has the same effects.
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- Hawrelak JA, Myers SP. Effects of two natural medicine formulations on irritable bowel syndrome symptoms: a pilot study. J Altern Complement Med. 2010 Oct;16(10):1065-71.
- Newall C, et al. Herbal Medicines: A Guide for Health-Care Professionals, 1st ed. London: Pharmaceutical Press; 1996.
- Tamayo C, et al. The chemistry and biological activity of herbs used in Flor-essence herbal tonic and Essiac. Phytotherapy Res 2000;14:1-14.
- 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 Feb;16(2):197-205.
- Choi HR, Choi JS, Han YN, et al. Peroxynitrite scavenging activity of herb extracts. Phytother Res. 2002 Jun;16(4):364-7.
- Brinker F. Herb Contraindications and Drug Interactions, 3rd ed. Sandy (OR): Eclectic Medical Publications; 2001.