Irritable Bowel Syndrome

What is Irritable Bowel Syndrome?

Irritable bowel syndrome (IBS) is functional gastrointestinal (GI) disorder of the colon. IBS is the most frequently diagnosed condition in gastroenterology, with some studies suggesting as many as 11-20 percent of the population in industrialized countries may have the condition (both diagnosed and undiagnosed).[1]

IBS is characterized by abdominal pain, bloating, cramping, bowel habit disturbances, and sometimes mucus in the stool. These changes are not explained by other structural or biochemical abnormalities. The presentation of IBS is highly variable and has been subcategorized into those who predominately have constipation (IBS-C), diarrhea (IBS-D), and alternating or mixed (IBS-M). IBS and is more common in women than men and while children can get the syndrome, it typically starts later in life (between the ages of 20-30).

Anxiety and depression are common co-morbidities.

Although IBS can be uncomfortable and painful, but it does not appear to damage the digestive system, nor does it tend to lead to other gastrointestinal disorders.

Causes and Symptoms

The cause of Irritable Bowel Syndrome is unknown. The common features appear to be hypersensitivity of musculature and/or nervous system of the digestive tract. Disturbances of the digestive system microbiome, which, in turn, affect the musculature and nervous system has been suggested as a cause of IBS.[2] Another area of investigation has been serotonin, which modulates motor and sensory functions in the digestive tract.[3] Stress, large meals, certain medications, certain foods, and alcohol have all been suggested as potential triggers for IBS. While

While many causes have been postulated, none has proven universally present in all patients with IBS. Some patients have disturbances of the microbiome, others do not; some are affected by stress, others are not… Future research may point to a universal underlying cause, or it may be that the cause is multifactorial or individual sensitivities lead to the condition.


No definitive diagnosis of Irritable Bowel Syndrome exists; the diagnosis consists of first ruling out other disorders (such as ulcerative colitis, Crohn’s disease, and others) and then using a set of criteria to arrive at a diagnosis.

There are two different sets of criteria used to help diagnose IBS (Rome Criteria are most often used):

  • Rome Criteria: For a diagnosis of IBS, these criteria require the presence of abdominal pain and discomfort lasting at least three days a month in the last three months AND two or more of the following: symptom improvement following defecation, altered frequency of stool, or altered consistency of stool.
  • Manning Criteria: These criteria focus on pain that is relieved by defecation, the sensation of incomplete bowel movements, mucus in the stool, and changes in stool consistency.

To help rule-out other conditions, the following may be part of the diagnostic workup:

  • Blood tests
  • Colonoscopy/Flexible Sigmoidoscopy
  • Hydrogen Breath tests
  • Lactose intolerance tests
  • Lower GI series
  • Stool tests
  • X-Ray or CT Scan

While often not included in a diagnostic workup, a lactose breath test is important consideration due to lactose intolerance is often mistaken for IBS, and is common (around 25 percent) in people presenting with IBS symptoms.[4]


Conventional Treatment

Since there are varying presentations of Irritable Bowel Syndrome, treatment is often personalized to the individual. For mild to moderate symptoms, conventional treatment suggests the use of a diary (recording food/stress/emotions) to help uncover factors that trigger symptoms. Stress management, including hypnosis, relaxation, and biofeedback may also be suggested. Eating smaller meals is another common recommendation.

Pharmacological Treatment:

  • Antidiarrheals: Synthetic opioids, such as Loperamide that act on intestinal musculature to prolong transit time and inhibit peristalsis, are used in people who tend towards diarrhea (IBS-D). While loperamide doesn’t appear to reduce pain associated with IBS (in fact, research shows it sometimes worsens pain), it does help to reduce frequency and solidify stool.[5]
  • Fiber: Bulking agents, such as psyllium or other fibers, along with plenty of water, are suggested for people who tend towards constipation. Fiber does not appear to help with bloating or pain associated with IBS,[6] but has a long history of use to help ease constipation.[7]
  • Antidepressants: Several reviews have suggested that antidepressants significantly decrease pain, IBS symptom scores, and overall global assessment in people with IBS. Sub-group analysis suggests that tricyclic antidepressants are the most reliable for pain reduction, but these medications are associated with a high number of adverse events.[8] Hypothetically, it has been suggested that selective serotonin reuptake inhibitors may be more useful for those with constipation (IBS-C) and tricyclics for those with diarrhea (IBS-D), but this remains to be determined in future research.[9]
  • Antispasmodics: There is some evidence that antispasmodics are effective for IBS, but the research is not consistent. A Cochrane review has suggested that cimetropium/dicyclomine, pinaverium and trimebutine may be helpful for reducing pain in IBS. [10]

Natural Approaches

Food Allergies

Studies suggest that for approximately one-quarter of IBS patients, symptoms may be initiated or exacerbated by one or more dietary constituents.[11] In a review of seven studies involving IBS , an elimination diet resulted in a positive response rate that ranged from 15-71 percent (depending on the study). Wheat, milk, and eggs were most commonly identified to exacerbate symptoms. Food allergy seems to be more common in people who suffer from diarrhea (IBS-D) rather than constipation (IBS-C).[12]

The mechanism by which food induces a mucosal immune response is uncertain, but IgE and IgF4 appear to be activated at least in a sub-set of IBS patients.[13]

With this in mind, it is reasonable to consider an allergy elimination diet for a period of time, especially in those in whom diarrhea predominates. A study that included a five-year follow-up for those who removed dairy foods demonstrated less visits for complaints by those avoided dairy for the full time period.[14]


Digestive Enzymes:

Studies suggest that substantial numbers of IBS patients have clinically unrecognized lactose malabsorption (approx. 24 percent, compared to 5 percent in general public) as confirmed by hydrogen breath test.[15] Other fermentable sugars (fructose) malabsorption has also been shown to have an effect in IBS symptoms.[16]

Primary symptoms of gas/bloating imply undigested fermentable foodstuffs and suggest that digestive enzymes may be helpful, but research is lacking. A small, one-day, study using pancreatic digestive enzymes, reported reductions in bloating, gas, and fullness following supplementation.[17]


It is clear from the majority of studies that fiber supplementation does not reduce the symptoms of IBS (pain, bloating).[18] Fiber, though, remains an effective tool for those who suffer from IBS with constipation (IBS-C). Insoluble fiber (corn wheat bran…) has been shown in some studies to worsen IBS symptoms,[19] so soluble fibers (psyllium, oat bran, flax seeds) are suggested.


The human gut is home to a complex community of microorganisms, this microbiome is just beginning to be recognized as an important modifier of health. Recent studies have suggested that disturbances in the microbiome may lead to alterations of gut barrier, including pathogen-binding abilities, modulation of gut inflammatory response, changes in gut motility, and increased hypersensitivity. Multiple large, placebo-controlled, studies have suggested improvement in flatulence, abdominal distension, pain, and reduction in composite IBS symptomology with the use of probiotics. [20],[21],[22]

Peppermint Oil

Peppermint tea, tincture, and oil have long been the cornerstone of IBS management for traditional and complimentary practitioners. Enteric-coated peppermint has largely replaced the other versions, and is now the focus of substantial research. Peppermint oil’s anti-spasmodic properties appear to be due to calcium channel blocking of intestinal smooth muscles. [23]

A typical regimen includes two enteric-coated capsules (180-200 mg) twice a day. Average positive response rates (include reductions in abdominal pain, discomfort, gas and bloating) are close to 60 percent.[24] A recent Cochrane review has confirmed peppermint oil as an effective antispasmodic.[25]A Journal of Pediatrics study found peppermint oil to be effective in children, where 75 percent of participants had reduced severity of pain associated with IBS[26]

Peppermint oil may be the first therapy of choice for those suffering from IBS, due to low side effects and general effectiveness.


[1] Kajander K, Myllyluoma E, Rajilić-Stojanović M, et al. Clinical trial: multispecies probiotic supplementation alleviates the symptoms of irritable bowel syndrome and stabilizes intestinal microbiota. Aliment Pharmacol Ther. 2008 Jan 1;27(1):48-57. Epub 2007 Oct 5. PMID: 17919270.

[2] Bixquert Jiménez M. Treatment of irritable bowel syndrome with probiotics. An etiopathogenic approach at last? Rev Esp Enferm Dig. 2009 Aug;101(8):553-64. PMID: 19785495.

[3] Camilleri M. Serotonin in the gastrointestinal tract. Curr Opin Endocrinol Diabetes Obes. 2009 Feb;16(1):53-9. PMID: 19115522.

[4] Vernia P, Di Camillo M, Marinaro V. Lactose malabsorption, irritable bowel syndrome and self-reported milk intolerance. Dig Liver Dis. 2001 Apr;33(3):234-9. PMID: 11407668.

[5] Hovdenak N. Loperamide treatment of the irritable bowel syndrome. Scand J Gastroenterol Suppl. 1987;130:81-4. PubMed PMID: 3306904.

[6] Ruepert L, Quartero AO, de Wit NJ, et al. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database Syst Rev. 2011 Aug 10;(8):CD003460. PMID: 21833945.

[7] Otles S, Ozgoz S. Health effects of dietary fiber. Acta Sci Pol Technol Aliment. 2014 Apr-Jun;13(2):191-202. PMID: 24876314.

[8] Ruepert L, Quartero AO, de Wit NJ, et al. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database Syst Rev. 2011 Aug 10;(8):CD003460. PMID: 21833945.

[9] Brandt LJ, Chey WD, Foxx-Orenstein AE, et al. An evidence-based position statement on the management of irritable bowel syndrome. Am J Gastroenterol. 2009 Jan;104 Suppl 1:S1-35. PMID: 19521341.

[10] Ruepert L, Quartero AO, de Wit NJ, et al. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database Syst Rev. 2011 Aug 10;(8):CD003460. PMID: 21833945.

[11] Heizer WD, Southern S, McGovern S. The role of diet in symptoms of irritable bowel syndrome in adults: a narrative review. J Am Diet Assoc. 2009 Jul;109(7):1204-14. doi: 10.1016/j.jada.2009.04.012. Review. PubMed PMID: 19559137.

[12] Niec AM, Frankum B, Talley NJ. Are adverse food reactions linked to irritable bowel syndrome? Am J Gastroenterol. 1998 Nov;93(11):2184-90. PMID: 9820394.

[13] Park MI, Camilleri M. Is there a role of food allergy in irritable bowel syndrome and functional dyspepsia? A systematic review. Neurogastroenterol Motil. 2006 Aug;18(8):595-607. PMID: 16918724.

[14] Böhmer CJ, Tuynman HA. The effect of a lactose-restricted diet in patients with a positive lactose tolerance test, earlier diagnosed as irritable bowel syndrome: a 5-year follow-up study. Eur J Gastroenterol Hepatol. 2001 Aug;13(8):941-4. PMID: 11507359.

[15] Böhmer CJ, Tuynman HA. The clinical relevance of lactose malabsorption in irritable bowel syndrome. Eur J Gastroenterol Hepatol. 1996 Oct;8(10):1013-6. PMID: 8930569.

[16] Nelis GF, Vermeeren MA, Jansen W. Role of fructose-sorbitol malabsorption in the irritable bowel syndrome. Gastroenterology. 1990 Oct;99(4):1016-20. PMID: 2394324.

[17] Suarez F, Levitt MD, Adshead J, Barkin JS. Pancreatic supplements reduce symptomatic response of healthy subjects to a high fat meal. Dig Dis Sci. 1999 Jul;44(7):1317-21. PMID: 10489912.

[18] Ruepert L, Quartero AO, de Wit NJ, et al. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database Syst Rev. 2011 Aug 10;(8):CD003460. PMID: 21833945.

[19] Bijkerk CJ, Muris JW, Knottnerus JA, Hoes AW, de Wit NJ. Systematic review: the role of different types of fibre in the treatment of irritable bowel syndrome. Aliment Pharmacol Ther. 2004 Feb 1;19(3):245-51. PMID: 14984370.

[20] Hungin AP, 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 Oct;38(8):864-86. doi: 10.1111/apt.12460. Epub 2013 Aug 27.PMID: 23981066.

[21] Wilhelm SM, Brubaker CM, Varcak EA, Kale-Pradhan PB. Effectiveness of probiotics in the treatment of irritable bowel syndrome. Pharmacotherapy. 2008 Apr;28(4):496-505. PMID: 18363533.

[22] Spiller R. Review article: probiotics and prebiotics in irritable bowel syndrome. Aliment Pharmacol Ther. 2008 Aug 15;28(4):385-96. PMID: 18532993.

[23] Alam MS, Roy PK, Miah AR, Mollick SH, Khan MR, Mahmud MC, Khatun S. Efficacy of Peppermint oil in diarrhea predominant IBS – a double blind randomized placebo – controlled study. Mymensingh Med J. 2013 Jan;22(1):27-30. PMID: 23416804.

[24] Grigoleit HG, Grigoleit P. Peppermint oil in irritable bowel syndrome. Phytomedicine. 2005 Aug;12(8):601-6. PMID: 16121521.

[25] Ruepert L, Quartero AO, de Wit NJ, et al. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database Syst Rev. 2011 Aug 10;(8):CD003460. PMID: 21833945.

[26] Kline RM, Kline JJ, Di Palma J, Barbero GJ. Enteric-coated, pH-dependent peppermint oil capsules for the treatment of irritable bowel syndrome in children. J Pediatr. 2001 Jan;138(1):125-8. PMID: 11148527.