Slippery elm (inner bark)

Over-the-counter botanical supplement, the inner bark of Ulmus rubra (slippery elm, a North American tree); a mucilage demulcent with traditional use for irritation of the gastrointestinal and throat mucosa

ATC code: A02BX-SLIPPERY-ELM (Slippery elm inner bark (Ulmus rubra))

Brand names – supplements

Nature's Way Slippery Elm Bark 400 mg, Thayers Slippery Elm Lozenges, Herb Pharm Slippery Elm Glycerite, Now Foods Slippery Elm 400 mg

Supplements are not tested in clinical trials and are not registered as medications.

Mechanism of action

Slippery elm (Ulmus rubra) is a tree native to the eastern United States. The medicinal part is the inner bark. The main component is high molecular weight mucilage polysaccharides that form a viscous slime on contact with water. Demulcent action: a mucilage layer coats the irritated mucosa of the pharynx, esophagus and stomach and mechanically protects it from chemical and physical irritants. There is almost no systemic absorption. Clinical RCTs are limited: a pilot study by Hawrelak (J Altern Complement Med 2010) in 21 patients with IBS showed moderate improvement in the constipation-predominant variant but without psyllium comparison or control. Large RCTs in IBD or gastritis are absent. HMPC has no separate monograph on Ulmus rubra; EMA HMPC covers only European elm species. NCCIH (NIH) 2020 describes slippery elm as an herbal product with traditional use and no quality evidence for specific diseases. AEMPS and AESAN classify the product as a complemento alimenticio without therapeutic indication. Market products include Nature's Way Slippery Elm, Now Foods Slippery Elm, Solaray Slippery Elm.

Indications

Esophageal mucosal irritation

Adjunct

Slippery elm is an over-the-counter botanical supplement with traditional use as a mucilage demulcent for irritation of the esophagus and throat. Clinical RCTs in esophageal irritation with a burning-relief endpoint do not exist; the proposed mechanism is mechanical coating of the mucosa with a viscous film. NCCIH 2020 describes slippery elm as a traditional use product without quality evidence. HMPC has no separate monograph on Ulmus rubra. AEMPS and AESAN classify the product as a complemento alimenticio without therapeutic indication. Standard care for esophageal irritation per CG184 and 2022 includes a drug history (especially doxycycline, bisphosphonates or NSAIDs without water), an empirical PPI course for 4-8 weeks and endoscopy for alarm symptoms or refractoriness. Slippery elm may be a mild symptomatic adjunct for light throat clearing and burning (for example after irritation from hot or spicy food), but for suspected GERD discuss with a gastroenterologist or family doctor – PPIs give systemic protection, demulcents give short local relief.

Sources

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Body detoxification and cleansing

Not recommended

Slippery elm inner bark is sold as a tea or powder for "detox" and "cleansing" the body of toxins. Studies have not shown convincing benefit for this use: there is no evidence base for detoxification with this plant. The idea of "flushing out toxins" with supplements is not supported, since the liver, kidneys and gut already handle normal metabolites and toxins. The bark is rich in mucilage and can coat mucous membranes, which is why it is studied for throat irritation and digestive discomfort, but that is a separate indication.

Sources

NCCIH (NIH): Slippery elm: scientific evidence and safety (2020)

Inflammatory bowel disease (IBD)

Not recommended

Slippery elm (Ulmus rubra) is a herbal remedy made from the tree's inner bark, promoted for inflammatory bowel disease (Crohn's disease, ulcerative colitis) as a gentle mucilaginous agent. No reliable evidence shows it helps in IBD – there's no evidence base for this use. What does work in IBD are treatments with proven benefit: aminosalicylates, corticosteroids for flares, immunosuppressants, and biologics prescribed by a gastroenterologist. The substance itself is harmless in this role, but don't use it instead of treatment with proven benefit – you could lose control of the disease.

Sources

Irritable bowel syndrome

Not recommended

In irritable bowel syndrome, slippery elm was studied in a single pilot trial. Hawrelak (J Altern Complement Med 2010) in 21 patients with IBS-C compared a herbal blend with slippery elm against no placebo control: a moderate symptom improvement was reported. This is not the level of a large blinded RCT. CG61 and IBS 2021 for IBS-C recommend psyllium (soluble fiber), linaclotide or plecanatide; for IBS-D – loperamide, rifaximin, eluxadoline; for mixed IBS – individualized selection. Slippery elm is not mentioned in the guidelines. There is no Cochrane review on slippery elm in IBS. AEMPS and AESAN classify the product as a complemento alimenticio without therapeutic indication. If slippery elm was bought «for IBS», discuss with a gastroenterologist – at the current evidence level the first line in IBS is drugs with proven efficacy and a low-FODMAP diet, and demulcents do not belong in this scheme.

Sources

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Safety

Contraindications

Known hypersensitivity to Ulmus rubra
Pregnancy (historical risk)
Oral drugs with narrow therapeutic window taken at the same time as slippery elm – mucilage may reduce absorption (separate by 1-2 hours)
Children under 6 years

Serious adverse effects

Reduced absorption of drugs with a narrow therapeutic window (levodopa, thyroxine, warfarin, digoxin)
Severe allergic reactions in sensitized users (rare)

Common adverse effects

Gastrointestinal discomfort, bloating
Nausea on an empty stomach
Skin rash in predisposed users

PregnancyFDA N

Slippery elm safety in human pregnancy has not been studied in RCTs. Historical use of slippery elm inner bark in the United States as an abortifacient has not been confirmed in modern studies but is concerning. NCCIH 2020 advises against use in pregnancy because of incomplete data. AEMPS and AESAN advise against supplements without therapeutic indication during pregnancy.

Breastfeeding

Lactation safety has not been studied in RCTs. No data on transfer of slippery elm components into human milk.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Slippery elm (inner bark) used for?

Slippery elm (inner bark) is evaluated for the following indications with varying evidence strength: Inflammatory bowel disease (IBD) (evidence tier D), Esophageal mucosal irritation (evidence tier D), Irritable bowel syndrome (evidence tier D). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Slippery elm (inner bark)?

Common side effects of Slippery elm (inner bark) (≥ 1 in 100): Gastrointestinal discomfort, bloating, Nausea on an empty stomach, Skin rash in predisposed users. See the Safety section for uncommon and serious reactions.

Is Slippery elm (inner bark) safe during pregnancy?

FDA category N. Slippery elm safety in human pregnancy has not been studied in RCTs. Historical use of slippery elm inner bark in the United States as an abortifacient has not been confirmed in modern studies but is concerning. NCCIH 2020 advises against use in pregnancy because of incomplete data. AEMPS and AESAN advise against supplements without therapeutic indication during pregnancy.

Is Slippery elm (inner bark) compatible with breastfeeding?

Lactation safety has not been studied in RCTs. No data on transfer of slippery elm components into human milk.

Who should not take Slippery elm (inner bark)?

Slippery elm (inner bark) is contraindicated in: Known hypersensitivity to Ulmus rubra; Pregnancy (historical risk); Oral drugs with narrow therapeutic window taken at the same time as slippery elm – mucilage may reduce absorption (separate by 1-2 hours); Children under 6 years. Full list in the Safety section.

Mechanism of action

Indications

Esophageal mucosal irritation

Adjunct

Sources

Safety

Contraindications

Known hypersensitivity to Ulmus rubra
Pregnancy (historical risk)
Oral drugs with narrow therapeutic window taken at the same time as slippery elm – mucilage may reduce absorption (separate by 1-2 hours)
Children under 6 years

Serious adverse effects

Reduced absorption of drugs with a narrow therapeutic window (levodopa, thyroxine, warfarin, digoxin)
Severe allergic reactions in sensitized users (rare)

Common adverse effects

Gastrointestinal discomfort, bloating
Nausea on an empty stomach
Skin rash in predisposed users

PregnancyFDA N

Breastfeeding

Lactation safety has not been studied in RCTs. No data on transfer of slippery elm components into human milk.

Calculate RID

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Frequently asked

What is Slippery elm (inner bark) used for?

What are the side effects of Slippery elm (inner bark)?

Is Slippery elm (inner bark) safe during pregnancy?

Is Slippery elm (inner bark) compatible with breastfeeding?

Lactation safety has not been studied in RCTs. No data on transfer of slippery elm components into human milk.

Who should not take Slippery elm (inner bark)?