Slippery elm may help to relieve minor cough or sore throat, but there is no clinical evidence to show that it is effective against infections, cancer or other serious medical conditions.
Although little laboratory research has been done with slippery elm per se, scientists are familiar with the effects of the fiber content in this bark extract. Slippery elm products contain mucilage, a sticky mixture of complex sugars that cannot be broken down by the human digestive tract. A formula containing slippery elm improved bowel habits and symptoms in patients with constipation-predominant irritable bowel syndrome. Mucilage also generally has a soothing effect when applied topically, and relieves cough and sore throat when taken by mouth, but these effects have not been shown specifically for slippery elm.
To treat coughs and bronchitis
The mucilage content in slippery elm is thought to relieve coughs and throat irritation, but human data are lacking.
To treat cancer
No scientific evidence supports this use.
To treat diarrhea
No scientific evidence supports this use. In fact, slippery elm may have laxative effects.
To treat irritable bowel syndrome (IBS):
One small clinical trial found that a formulation containing slippery elm improved bowel habits and symptoms in patients with constipation-predominant IBS. However, further study is needed to confirm this effect.
Topically, to treat skin abscesses and ulcers
The mucilage content in slippery elm is thought to have a soothing effect when applied topically, but human data are lacking.
Do Not Take If
You are taking any other medications by mouth at the same time: In theory, the high fiber content of slippery elm can reduce the absorption of other drugs taken at the same time, thereby reducing their effectiveness.
Slippery elm appears to be safe for coughs and minor gastrointestinal complaints, but it should not be used to treat cancer or bronchitis.
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.
Mechanism of Action
Mucilage in slippery elm is responsible for its 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).