Irritable Bowel Syndrome (IBS) is a chronic health condition that health care providers should be prepared to identify and help their patients with. This gastrointestinal (GI) disorder affects 7-16% (roughly 30 million) people in the US and 11% of all people world-wide.^1-4 As awareness increases and diagnostic criteria are updated, some studies indicate that IBS is becoming diagnosed more often than previously. Researchers also hypothesize that rates may also be increasing post-pandemic related to the virus that causes COVID-19 and/or the associated stress of going through a pandemic.⁵ IBS can be categorized based on the type of gastrointestinal GI dysfunction including IBS with diarrhea (IBS-D), IBS with constipation (IBS-C), IBS mixed (IBS-M) and is often accompanied by bloating and pain.^1,2,6 Data shows that IBS affects women slightly more often than men (55% and 45% respectively) and the average age that a patient develops their first symptoms is before 40 with onset of symptoms less likely in people 50 or older.^1,7,8

There isn’t one single diagnostic test for IBS, creating challenges for health care practitioners and patients alike. Current guidelines are based on a collection of symptoms including bowel dysfunction in addition to pain or discomfort.^1,4,6,8-11 Therapies commonly prescribed for people with IBS include pharmaceuticals and supplements from fiber and osmotic laxatives for IBS-C, antidiarrheal agents, non-systemic antibiotics such as rifaximin for IBS-D, antispasmodics or peppermint oil for pain as well as dietary interventions such as the low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet and gut microbiome modification through fiber, probiotic foods or supplementation.^{1-4,7,8,12-14}

The mechanism behind IBS is complex. Many experts believe that it is a gut-brain interaction disorder that correlates with the central nervous system (CNS) and is mediated by visceral hypersensitivity. GI motor and sensory problems, chronic, low-grade inflammation of the digestive tract, problems with GI motility, bile acid malabsorption, and the gut microbiome also may be involved.^1-4,7,11,12 Dietary strategies should be personalized for each patient and range from increasing to decreasing or altering the type of fiber a person consumes and may also focus on probiotic foods or supplements. IBS treatment requires a multidisciplinary approach and is a critical place for health care providers to offer their expertise and support.

Dietary Interventions for IBS

A strategic and personalized approach to IBS is a critical place for health care providers to support their clients. From assessing potential triggers in the diet to strategizing how to alter fibrous food intake (increasing or decreasing) or increase probiotics from food or supplements, diet is important. The low FODMAP diet is one of the most studied and common elimination diets used in people with IBS but there are several possible approaches and there are other dietary strategies to consider as well. 

The Low FODMAP Diet

By reducing certain categories of short-chain fermentable carbohydrates, the low FODMAP diet could help reduce intestinal osmolarity, water volume, and gas production, helping to control symptoms.^2,11 FODMAPs are found in some fruits, vegetables, dairy (lactose), artificial sweeteners, honey and agave, and wheat.¹¹ A recent review and meta-analysis including 12 papers (n=722) found that a low FODMAP diet reduced severity of IBS symptoms by a moderate to large amount and also increased quality of life when compared to a standard control diet.² Several other large studies on a low FODMAP diet for IBS symptoms found up to a 70% reduction of pain and bloating.¹¹

The low FODMAP diet is actually an elimination diet that should be run for six to eight weeks at which time specific FODMAP groups should be systematically added back in and ‘tested’ while tracking symptoms to help identify problematic foods for the patient.² The low FODMAP diet is one of the most highly recommended and evidence-based diets for IBS but it’s restrictive and may affect quality of life while in the elimination phase.² Studies suggest that patients are more likely to experience nutritional deficiencies, anxiety, disordered eating, and decreased quality of life if they are self-directed without their physician and dietitian to support them.¹⁵

Other Dietary and Lifestyle Strategies for IBS

The low FODMAP diet can be confusing and hard to follow for many people. There are other dietary and lifestyle strategies that have proven benefits though many need more research to elucidate their potential for improving symptoms. An important study on patients with IBS-C compared three groups (n=33 each) who received traditional dietary advice (eating regular, balanced meals, adequate hydration, reducing caffeine, alcohol, and sugar sweetened beverages, high fat, spicy, or fried foods, and limiting fruits and high-gas foods such as beans), a low FODMAP diet, or a gluten-free diet.¹³ All of the groups experienced significant improvements in their individual symptoms but notably, there was no significant difference between groups.¹³ The traditional dietary advice group found their diet more affordable, less time consuming, and easier to follow when eating with others.¹³ A 2024 unblinded clinical trial (n=48) compared a group following the Mediterranean diet vs a habitual diet for six weeks and found improvements in both GI and psychological symptoms in the intervention group offering another possible beneficial dietary plan.¹⁶

Probiotics, fermented foods, fiber, and supplements have also been studied for IBS though current research is limited. Studies indicate that consuming fermented foods or taking probiotic supplements may inhibit, displace, or interfere with the way pathogenic gut microbes adhere to the gut lining, supporting a healthy intestinal barrier and possibly helping reduce IBS symptoms.^4,7,11,17  Specific probiotics such as VSL#3 have been shown to therapeutically reduce colonic permeability and IBS-associated abdominal pain in clinical trials.¹⁸ Soluble, prebiotic fiber such as psyllium has been used to reduce bloating, abdominal distention, and gas while ground flaxseed has also been shown to improve stool consistency in people with IBS. Researchers hypothesize that these prebiotic fibers may improve gut function and the gut microbiome environment because they are a preferred energy source for more favorable bacteria that appear to be protective against IBS such as Bacteroidetes, Bifidobacterium, Faecalibacterium prausnitzii, and genera Coprococcus and Anaerostipes.^4,8-10 The gut microbiome also creates metabolites such as short chain fatty acids including butyrate which has shown positive effects on IBS symptoms in some studies regarding decreased inflammation and better intestinal integrity, motility, and improved immunity.¹⁰

Psychotherapy support including stress reduction techniques are advised as a first line therapy for IBS. Because of the likelihood that IBS has a gut-brain connection and many patients notice a worsening of symptoms with stress or anxiety, health care providers should screen and refer out or treat mental health (depending on their scope of practice) for all patients with IBS.^1,3 A large review of articles on psychotherapy and IBS (n=28 articles) found that cognitive behavior therapy significantly reduced IBS symptom severity, frequency, and pain. Both mindfulness and hypnotherapy were also successful at improving symptoms.³ A very large prospective analysis (n=362,193) also found that both sedentary behavior and lower sleep duration ≤7 hours per day were significantly associated with IBS incidence.¹⁶

Key Takeaways for Practitioners 

Health care practitioners should create an individualized treatment plan that offers reassurance, provides education, and builds a positive relationship with their patients.
Practitioners should target each patient’s most bothersome symptoms which, depending on scope of practice, could include pharmaceuticals or supplements, as well as dietary education and psychological support for living with problematic symptoms or treating underlying stress and anxiety that could make it worse.^1,3,4

From dietitians to physical therapists, nurses, doctors, and all other allied health professionals, seeking ongoing professional education and resources may be needed as IBS can be encountered in any clinical setting and with otherwise healthy patients as well.²⁰ IBS patient interviews have shown that patients seek clear and open communication from their providers as well as collaboration from an interdisciplinary team.²⁰ Developing trust, validating patients’ lived experiences, and empathy should be a hallmark of IBS patient care.

References:

1. Camilleri M. Diagnosis and treatment of irritable bowel syndrome: a review. JAMA. 2021;325(9):865-77.
2. van Lanen AS, de Bree A, Greyling A. Efficacy of a low-FODMAP diet in adult irritable bowel syndrome: a systematic review and meta-analysis. European journal of nutrition. 2021;60:3505-22.
3. Slouha E, Patel B, Mohamed A, Razeq Z, Clunes LA, Kollias TF. Psychotherapy for Irritable Bowel Syndrome: A Systematic Review. Cureus. 2023;15(12).
4. Black CJ, Ford AC. Best management of irritable bowel syndrome. Frontline Gastroenterology. 2021;12(4):303-15.
5. Almario CV, Sharabi E, Chey WD, Lauzon M, Higgins CS, Spiegel BM. Prevalence and Burden of Illness of Rome IV Irritable Bowel Syndrome in the United States: Results from a Nationwide Cross-Sectional Study. Gastroenterology. 2023;165(6):1475-87.
6. Lacy BE, Patel NK. Rome Criteria and a Diagnostic Approach to Irritable Bowel Syndrome. J Clin Med. 2017;6(11):99.
7. Simon E, Călinoiu LF, Mitrea L, Vodnar DC. Probiotics, prebiotics, and synbiotics: Implications and beneficial effects against irritable bowel syndrome. Nutrients. 2021;13(6):2112.
8. Sperber AD. epidemiology of IBS and other bowel disorders of gut–brain interaction (DGBI). Alimentary Pharmacology & Therapeutics. 2021;54:S1-1.
9. Agnello M, Carroll LN, Imam N, et al. Gut microbiome composition and risk factors in a large cross-sectional IBS cohort. BMJ open gastroenterology. 2020;7(1):e000345.
10. Jiang W, Wu J, Zhu S, Xin L, Yu C, Shen Z. The Role of Short Chain Fatty Acids in Irritable Bowel Syndrome. J Neurogastroenterol Motil. 2022;28(4):540-548.
11. Galica AN, Galica R, Dumitrașcu DL. Diet, fibers, and probiotics for irritable bowel syndrome. J Med Life. 2022;15(2):174-179.
12. Paine P. current and future treatment approaches for pain in IBS. Alimentary Pharmacology & Therapeutics. 2021;54:S75-88.
13. Rej A, Sanders DS, Shaw CC, Buckle R, Trott N, Agrawal A, Aziz I. Efficacy and acceptability of dietary therapies in non-constipated irritable bowel syndrome: a randomized trial of traditional dietary advice, the low FODMAP diet, and the gluten-free diet. Clinical gastroenterology and hepatology. 2022;20(12):2876-87.
14. Black CJ, Burr NE, Camilleri M, et al. Efficacy of pharmacological therapies in patients with IBS with diarrhoea or mixed stool pattern: systematic review and network meta-analysis. Gut. 2020;69(1):74-82.
15. Simons M, Taft TH, Doerfler B, et al. Narrative review: Risk of eating disorders and nutritional deficiencies with dietary therapies for irritable bowel syndrome. Neurogastroenterology & Motility. 2022;34(1):e14188.
16. Staudacher HM, Mahoney S, Canale K, et al. Clinical trial: A Mediterranean diet is feasible and improves gastrointestinal and psychological symptoms in irritable bowel syndrome. Alimentary Pharmacology & Therapeutics. 2024;59(4):492-503.
17. Spiller R. Impact of diet on symptoms of the irritable bowel syndrome. Nutrients. 2021;13(2):575.
18. Boonma P, Shapiro JM, Hollister EB, et al. Probiotic VSL# 3 treatment reduces colonic permeability and abdominal pain symptoms in patients with irritable bowel syndrome. Frontiers in Pain Research. 2021;2:691689.
19. Gao X, Tian S, Huang N, Sun G, Huang T. Associations of daily sedentary behavior, physical activity, and sleep with irritable bowel syndrome: A prospective analysis of 362,193 participants. Journal of Sport and Health Science. 2024;13(1):72-80.
20. Masclee GM, Snijkers JT, Boersma M, Masclee AA, Keszthelyi D. Patient preferences of healthcare delivery in irritable bowel syndrome: a focus group study. BMC gastroenterology. 2021;21:1-8.