CAMs for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a common disorder affecting the small intestine and colon.

There is no underlying structural or biochemical explanation for the symptoms, and the pathophysiology of IBS is not fully understood. Symptoms include abdominal pain, bloating and distension and altered bowel habits (chronic diarrhoea or constipation, or alternating between the two).

Treatment of IBS must be individualised according to the patient’s symptoms, and may include dietary modifications, psychological therapies and medicines.

Three complementary medicine options for treating IBS are peppermint, STW5 and probiotics.


What is it?

Mentha piperita is a plant from the mint family. Peppermint oil, extracted from the leaves, relaxes gastrointestinal smooth muscle and relieves flatulence when taken orally. Menthol is a main active constituent.

Evidence for IBS

A 2013 systematic review of nine RCTs (n = 726) found peppermint oil significantly superior to placebo for improvement of IBS symptoms. The authors concluded that peppermint oil is a safe and effective short-term treatment for IBS.1

Suggested counselling advice

Oral peppermint oil can cause gastrointestinal upset (e.g. nausea, heartburn, diarrhoea) and (rarely) hypersensitivity reactions, including skin rash and headache.2,3

Peppermint tea can reduce iron absorption. People at risk of iron deficiency should be advised to avoid drinking the tea with and for an hour after meals, and to take iron supplements and the tea at least 2 hours apart.4


What is it?

STW5 (Iberogast) is a proprietary liquid blend of nine herbs, including chamomile, liquorice, peppermint, milk thistle and Iberis amara.5

Evidence for IBS

A 2004 RCT (n = 208) found that 4 weeks’ treatment with STW5 was well tolerated and effective in alleviating IBS symptoms.5,6

Australian guidelines suggest that STW5 may relieve abdominal pain associated with IBS.7

Suggested counselling advice

Chamomile can cause allergic reactions. The risk is higher if you are allergic to other plant pollens.3,8 If you experience signs of a severe allergic reaction (e.g. hives, mouth tingling, stomach pain, difficulty breathing or swelling of face, tongue or throat) seek immediate medical attention. Chamomile may also act as a uterine stimulant in pregnancy.3


What are they?

Probiotics are live micro-organisms that, when administered in adequate amounts, confer a health benefit on the host.

The most commonly used and studied probiotics are species of Lactobacillus and Bifidobacterium bacteria.9

Probiotics have the ability to survive human gastrointestinal transit, adhere to the intestinal mucosa and colonise the intestinal tract. Proposed actions include inhibiting intestinal pathogens, enhancing the intestinal environment and mucosal function, and modulating host immune responses.9,10

Probiotic research is complicated by the wide variety of probiotic strains available. Generally, only a few probiotic strains have been studied for a particular health condition. Different strains may have some similar actions (e.g. reducing colon pH) that deliver similar health benefits. However, a specific strain may also have some unique actions that deliver unique health benefits. The probiotic formulation and dosage, and the age and health of the target patient group add further sources of variation in probiotic effects.9,11

Evidence for IBS

A 2016 British Dietetic Association systematic review assessed nine systematic reviews (35 RCTs; n = 3,406; 29 different dose-specific probiotic formulations) of probiotics for IBS in adults. The review found that no strain- or dose-specific probiotic was consistently effective to improve any IBS symptoms or quality of life. Specific probiotic recommendations for IBS management were not possible.12

The 2017 World Gastroenterology Organisation Global Guidelines advise that studies have consistently reported that probiotics reduce abdominal bloating and flatulence in IBS, and some probiotic strains relieve abdominal pain and overall symptoms.9

Australian guidelines advise that probiotics benefit some patients with IBS, but there is little evidence to guide probiotic choice or the patients most likely to benefit. The best (but weak) evidence is for Bifidobacterium spp. The guidelines recommend 4 weeks of treatment.7

Suggested counselling advice

Probiotics may improve some gastrointestinal symptoms within a few days. If you are using probiotics for a chronic gastrointestinal problem (e.g. IBS), you should take them every day for at least a month.11,13

Store according to the manufacturer’s instructions; some probiotics must be refrigerated.

Learn more

For more evidence-based information about these and other complementary medicines – including clinical notes on adverse effects, contraindications and interactions, as well as full references, refer to the Australian Pharmaceutical Formulary and Handbook 24th edition (APF24). APF is available in print or digital formats. Digital APF is available at (subscription required).


  1. Khanna R, Macdonald JK, Levesque BG. Peppermint oil for the treatment of irritable bowel syndrome: a systematic review and meta-analysis. J Clin Gastroenterol 2013. Epub 2013 Oct 4.
  2. Brayfield A, ed. Martindale: the complete drug reference. London: Pharmaceutical Press.
  3. Royal Pharmaceutical Society of Great Britain. Herbal medicines. 4th edn. London: Pharmaceutical Press; 2013.
  4. Williamson E, Driver S, Baxter K, eds. Stockley’s herbal medicines interactions. 2nd edn. London: Pharmaceutical Press; 2013.
  5. Ottillinger B, Storr M, Malfertheiner P, et al. STW 5 (Iberogast): a safe and effective standard in the treatment of functional gastrointestinal disorders. Wien Med Wochenschr 2013;163(3– 4):65–72.
  6. Madisch A, Holtmann G, Plein K, et al. Treatment of irritable bowel syndrome with herbal preparations: results of a double-blind, randomized, placebo-controlled, multi-centre trial. Aliment Pharmacol Ther 2004;19(3):271–9.
  7. eTG complete. Melbourne: Therapeutic Guidelines; 2017.
  8. Gregory PJ. Natural medicines. 2017. At:
  9. Guarner F, Sanders ME, Eliakim R, et al. World Gastroenterology Organisation global guidelines. probiotics and prebiotics. 2017.
  10. Goldenberg JZ, Lytvyn L, Steurich J, et al. Probiotics for the prevention of pediatric antibiotic-associated diarrhea. Cochrane Database of Systematic Reviews 2015, Issue 12.
  11. Hungin APS, Mulligan C, Pot B, et al. Systematic review: probiotics in the management of lower gastrointestinal symptoms in clinical practice – an evidence-based international guide. Aliment Pharmacol Ther 2013;38(8):864–86.
  12. McKenzie YA, Thompson J, Gulia P, et al. British Dietetic Association systematic review of systematic reviews and evidence-based practice guidelines for the use of probiotics in the management of irritable bowel syndrome in adults (2016 update). J Hum Nutr Diet 2016;29(5):576–92.
  13. Braun L, Cohen M. Herbs and natural supplements: an evidence-based guide. 4th edn. Chatswood: Elsevier; 2015.