Slippery Elm

Slippery elm is one of the least restricted ingredients on Australia's permitted list, and also one of the least studied. These are the questions our naturopaths ask in store, and most are about timing and what else you take.

A good fit if

• You're an adult and you're comfortable that it's based on how it works and long traditional use, not trial data
• You can take it a couple of hours apart from anything else you take
• You want the powder and don't mind a thick, slippery drink
• You'll check the botanical name on the label, or ask us to

Check with us first if

• You take any prescription medicine. Mucilage forms a thick gel in your gut, and nobody has measured whether that changes how other medicines are absorbed. Taking them a couple of hours apart is an easy precaution.
• You're being treated for Crohn's disease or ulcerative colitis. A published review of herb-drug interactions in older people with bowel disease names slippery elm, but we couldn't access its conclusion. Raise it with your gastroenterologist.
• You're pregnant or breastfeeding. There's no data either way and no official warning to go on. Folk claims point in both directions and we couldn't verify any of them, so we won't repeat them.
• It's for a child. We haven't found any data in children, and Australian labelling for a cough claim requires adults only, or medical advice for children under 2.
• Your symptoms are persistent, severe or new. Heartburn, bowel changes and a sore throat that won't settle all deserve a proper check rather than a supplement.

• Slippery elm bark powder, stirred into water. Best known for: The traditional preparation, and the one that matches how it works. Absorption: It isn't about absorption. The mucilage works by contact, and it's in contact from the first mouthful. Typical use: Item 4548, and the only slippery elm entry that's also allowed as an inactive ingredient, as well as active and homoeopathic.
• Slippery elm bark dry, and Ulmus rubra by its botanical name. Best known for: The same plant under the two other names you'll see on a label. Absorption: As above. Typical use: Items 4547 and 5089. If a label gives you a botanical name rather than a common name, Ulmus rubra is the one to look for.
• Capsules and tablets. Best known for: Convenience, and no texture to get past. Absorption: The gel forms in the stomach rather than coating your throat and oesophagus on the way down. Typical use: No study compares formats, so that's reasoning from how it works rather than evidence, and we'd rather say so.
• Lozenges. Best known for: Keeping the mucilage in contact with your throat for longer. Absorption: The same physical idea, working higher up. Typical use: For the throat rather than the gut. Again, this is based on how it works, because nobody has tested it.
• Multi-herb gut or detox blends. Best known for: Slippery elm as one name on a long list. Absorption: Impossible to know, because the dose of each ingredient usually isn't disclosed. Typical use: The blend in the trial also contained senna and cascara sagrada, both stimulant laxatives, so any gut effect is at least as likely to come from them.
• Other permitted elms: americana, campestris, glabra, minor, parvifolia, pumila. Best known for: They're different species that share a genus and nothing else. Absorption: Not applicable. Typical use: Items 5083 to 5088. None of them is slippery elm, and none of slippery elm's history belongs to them.
• Ulmus macrocarpa and Ulmus davidiana. Best known for: The two elms that do have clinical trials. Absorption: Not applicable. Typical use: Neither is anywhere in Schedule 1, and one of those studies used an injection rather than a supplement. That research doesn't carry over here.

Reference values. None. Slippery elm is a herb, not a nutrient, so there's no NHMRC recommended intake for it.

Typical supplemental range. There isn't a studied dose to share. No trial has tested slippery elm on its own, and we haven't found a reliable source for a traditional amount, water volume or mixing method either. Follow the directions on your product's label.

Upper level. Australia's permitted ingredients list (Schedule 1) sets no daily dose limit and no restriction on how it's taken (items 4547, 4548 and 5089), and no maximum intake has been set by the NHMRC, FSANZ or the TGA.

Worth knowing. The only dose figure we've found is 1,350 mg a day of an eight-herb blend, and slippery elm's share wasn't disclosed, so it tells you nothing about slippery elm itself. Because there's no official limit, our advice here is based on care rather than a rule, which is a reason to take more care, not less. What you need depends on your age, diet and health, so talk to one of our naturopaths.

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Prescription medicines. Mucilage forms a gel in the gut, and no source measures how it affects absorption of medicines. Taking them at different times is a precaution, not a measured one.
• Inflammatory bowel disease treated with medicine. A 2017 review of herb-medicine interactions discusses Ulmus rubra, but the summary we have doesn't include its slippery elm findings.
• Pregnancy and breastfeeding. There's no human data and no Schedule 1 pregnancy warning. That means unknown, not safe, and unverified folk claims point both ways.
• Children. The ingredient has no age restriction and there's no data in children, and cough claims require adults only, or medical advice under 2 years.
• Sudden tummy pain, nausea, vomiting or diarrhoea. Bowel-regularity claims require a statement telling you not to use it.
• Fluids. Bowel-regularity claims require a statement to drink plenty of water, which is standard for anything that adds bulk.
• Everyone. Schedule 1 sets no warning, limit or condition here, so every caution is our judgement rather than a legal requirement.
• Swapped species. Nine Ulmus entries are allowed and only three are slippery elm.