The educational content in this post, elaborated in collaboration with Bromatech, was independently developed and approved by the GMFH publishing team and editorial board.

The gut microbiota and the management of IBS

Irritable Bowel Syndrome (IBS) is recognized as a chronic, multifaceted disorder of gut-brain interaction (DGBI), characterized by recurrent abdominal pain related to defecation and may be associated with changes in bowel habits (diarrhea or constipation).1

The intestinal microbiota is suggested to be an underlying element explaining key pathophysiological alterations well described and studied in IBS, such as visceral hypersensitivity, impaired intestinal barrier function, altered intestinal secretion, and activation of the mucosal immune system with low-grade inflammatory response.2 This is supported not only by the known role of an acute infectious event in PI-IBS development but also by multiple pieces of evidence that gut microbiota modifying treatments (e.g., prebiotics, probiotics, antibiotics, or fecal microbiota transplantation) can improve IBS symptoms without significant side effects.3

The gastrointestinal tract is functionally connected to the central nervous system (CNS) through the enteric nervous system (ENS), composed of millions of neuronal cells located both in myenteric and submucosal plexuses. Many studies describe the possible mechanism of communication between gut microbiota and CNS as well as ENS, including the production of microbial-derived intermediates (e.g., SCFAs, tryptophan metabolites, secondary bile acids)4-6, regulation of intestinal barrier and tight junction integrity7,8, modulation of the enteric sensory afferents, in particular interactions with vagus nerve endings9, and mucosal immune regulation.

 

Evidence for probiotics and prebiotics in IBS

Specific probiotic strains and formulations may be beneficial in improving IBS symptoms, including bloating and abdominal pain, while the certainty in the evidence is low to very low due to the heterogeneity of patients with IBS and high variability of products between studies10. Probiotics appeal to patients because they are thought to be more “natural,” easier to obtain, and have fewer or no risk of negative effects than pharmaceutical medications (such as antidepressants). Patients with IBS are likely to be aware of probiotic products since they are readily available as over-the-counter medicines11.

In particular, a clinically important benefit might be achieved in certain subgroups of patients, particularly those with diarrhea-predominant symptoms (IBS-D) and those with constipation-predominant symptoms (IBS-C). There is evidence of the effectiveness of several probiotic strains from the following species (used in single-strain or multi-strain products)10,12:

  • Enterococcus faecium
  • Saccharomyces boulardii
  • Bifidobacterium bifidum, Bifidobacterium longum, Bifidobacterium animalis lactis
  • Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus plantarum, Lactobacillus rhamnosus
  • Escherichia coli

 

Therefore, it is reasonable to assume that many gastroenterologists and other medical professionals who treat patients with these conditions use or may be interested in utilizing probiotics, and that this interest may grow over time as new products are introduced. However, TV adverts, followed by family, friends, and the internet in general are the most common source of information for probiotics in gut health, while healthcare professionals are the least preferred source13.

Prebiotics can also help manage IBS symptoms in some patients. Indeed, intermittent prebiotic administration at low doses might be an alternative to continuous dietary restrictions such as the low FODMAP diet for patients with functional gut symptoms14.

 

Other interventions for IBS

For managing IBS, several drugs, mainly neuromodulators (low dosage of antidepressant) have shown efficacy in reducing symptoms and should be considered as a key treatment.15 Moreover, patients with IBS may be frustrated to see that medical examinations do not detect an organic source of their discomfort or that some drug does not relief their symptoms. For these reasons, they often recourse to complementary and alternative medicine to improve their symptoms, other than probiotics and antibiotics. Even if other natural supplements that are not probiotics could also be taken into consideration in the management of patients with IBS, for some of them the evidence is still inadequate16-18:

  • Peppermint oil: renowned for its antispasmodic properties, which can help ease intestinal muscle tension, potentially reducing global symptoms of IBS-particularly abdominal pain, and bloating- and also global symptoms of functional dyspepsia.
  • STW-5: This is a multi-herbal preparation that may help alleviate IBS symptoms by influencing gastrointestinal motility.
  • Glutamine: This amino acid is thought to aid the intestinal barrier integrity, with its possible beneficial effects in patients with IBS, in particular for patients with IBD-S with intestinal hyperpermeability following an enteric infection. However, the evidence is still limited.
  • Aloe Vera: While aloe vera is often used for its calming qualities, particularly in conditions like sunburn, its efficacy in IBS is less certain, with a possible higher benefit in patients with constipation-predominant IBS.
  • Melatonin: Mainly recognized for its function in controlling sleep. Melatonin has also been studied for IBS, particularly due to its potential effects on gastrointestinal motility and its role in the gut-brain axis.

 

Take-home messages:

  • IBS is a disorder of the gut-brain interaction, which is characterized by recurrent abdominal pain related to defecation.
  • Significant progress in understanding the key mechanisms of IBS has been achieved, largely due to increased research focus on the role of gut microbiota and the concept of dysbiosis.
  • Gut microbiota-modifying treatments, such as prebiotics and probiotics, can improve IBS symptoms without significant side effects.
  • Other non-prescription therapeutics that might help improve IBS symptoms, partly through changes in the gut microenvironment, are peppermint oil, STW-5, glutamine, aloe vera and melatonin, with a variable degree of efficacy.

 

References

  1. Ford AC, Sperber AD, Corsetti M, Camilleri M. Irritable bowel syndrome. The Lancet 2020; 396: 1675–1688. [DOI: 10.1016/S0140-6736(20)31548-8]
  2. Bhattarai Y, Muniz Pedrogo DA, Kashyap PC. Irritable bowel syndrome: a gut microbiota-related disorder? American Journal of Physiology-Gastrointestinal and Liver Physiology 2017; 312: G52–G62. [DOI: 10.1152/ajpgi.00338.2016]
  3. Barbara G, Grover M, Bercik P, Corsetti M, Ghoshal UC, Ohman L, Rajilić-Stojanović M. Rome Foundation Working Team Report on Post-Infection Irritable Bowel Syndrome. Gastroenterology 2019; 156: 46-58.e7. [DOI: 10.1053/j.gastro.2018.07.011]
  4. Zeng H, Umar S, Rust B, Lazarova D, Bordonaro M. Secondary Bile Acids and Short Chain Fatty Acids in the Colon: A Focus on Colonic Microbiome, Cell Proliferation, Inflammation, and Cancer. Int J Mol Sci 2019; 20: 1214. [DOI: 10.3390/ijms20051214]
  5. Dalile B, Van Oudenhove L, Vervliet B, Verbeke K. The role of short-chain fatty acids in microbiota–gut–brain communication. Nat Rev Gastroenterol Hepatol 2019; 16: 461–478. [DOI: 10.1038/s41575-019-0157-3]
  6. Agus A, Planchais J, Sokol H. Gut Microbiota Regulation of Tryptophan Metabolism in Health and Disease. Cell Host Microbe 2018; 23: 716–724. [DOI: 10.1016/j.chom.2018.05.003]
  7. Anderson RC, Cookson AL, McNabb WC, Kelly WJ, Roy NC. Lactobacillus plantarum DSM 2648 is a potential probiotic that enhances intestinal barrier function. FEMS Microbiol Lett 2010; 309: 184–92. [PMID: 20618863 DOI: 10.1111/j.1574-6968.2010.02038.x]
  8. Putaala H, Salusjärvi T, Nordström M, Saarinen M, Ouwehand AC, Bech Hansen E, Rautonen N. Effect of four probiotic strains and Escherichia coli O157:H7 on tight junction integrity and cyclo-oxygenase expression. Res Microbiol 2008; 159: 692–8. [PMID: 18783733 DOI: 10.1016/j.resmic.2008.08.002]
  9. Bravo JA, Forsythe P, Chew M V., Escaravage E, Savignac HM, Dinan TG, Bienenstock J, Cryan JF. Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve. Proceedings of the National Academy of Sciences 2011; 108: 16050–16055. [DOI: 10.1073/pnas.1102999108]
  10. Goodoory VC, Khasawneh M, Black CJ, et al. Efficacy of probiotics in irritable bowel syndrome: systematic review and meta-analysis. Gastroenterology. 2023; 165(5):1206-1218. doi: 10.1053/j.gastro.2023.07.018.
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