A low FODMAP diet is frequently used for managing irritable bowel syndrome (IBS). Individualised management is best done in conjunction with a dietitian well-versed in IBS for proper assessment and explanation of IBS pathophysiology and appropriate therapies while still ensuring nutritional adequacy. Best treatment for IBS will depend on the pathophysiological basis for symptom genesis. IBS is heterogeneous, with four known possible abnormalities: visceral hypersensitivity, altered motility, enhanced symptom perception and altered microbiome.
Visceral hypersensitivity: a low FODMAP diet is mainly targeted for this patient group, with a 75% rate of efficacy. A dietitian may also recommend antispasmodic agents, including peppermint oil. Another dietary treatment is a low food chemical diet, although this diet is often extremely limited, and therefore, not suited for some populations.
Altered motility: in patients with fast transit, a dietitian may recommend a reduction in all FODMAPs or targeted mono- and disaccharides, which are more osmotic in nature. If not effective, patients may benefit from psyllium, which has an exceptional water-holding capacity aimed to promote more formed stools. Patients with slow/un-coordinated transit are often more difficult to treat. Dietary interventions have some success and usually comprise a combination of adequate fibre and increased fluid, osmotic laxatives (including FODMAPs) and stimulating agents such as coffee, senna and exercise.
Enhanced symptom perception: cognitive behavioural therapy and gut-directed hypnotherapy both have rates of efficacy similar to that seen with a low FODMAP diet.
Altered microbiome: supplementary probiotics and prebiotics have weak evidence of efficacy with some notable exceptions. A dietitian may trial supplementary Bifidobacterium infantis 35624 or inulin, usually as an adjunct therapy.
A dietitian’s toolbox will encompass dietary methods to treat IBS, but additionally identify where dietary treatment is not indicated to ensure that diet is correctly used and patients are not nutritionally or psychologically compromised.