Initial dietary therapy for irritable bowel syndrome

Many patients strongly associate irritable bowel syndrome (IBS) symptoms with ingestion of certain foods or irregular eating patterns.

Explore the dietary history of patients who present with symptoms of IBS. Patients should complete a food diary and be assessed for common triggers of food intolerance, irregular eating patterns and nutritional adequacy.

For patients with irregular eating patterns, regular meal times and portion control can assist bowel regularity and symptom control.

Food intolerance is increasingly being recognised as a contributory factor in IBS, and its role in the pathogenesis and precipitation of symptoms is being explored. Food intolerance is generally not the cause of IBS but is a trigger for symptoms. See Food intolerance for information about the symptoms and diagnosis of food intolerance. Common triggers of food intolerance include:

• caffeine
• alcohol
• carbonated drinks
• fatty food
• fibre
• lactose-containing food
• wheat
• spicy food.

These triggers produce similar physiological changes (ie small bowel distension and fluid retention) in healthy individuals and those with IBS; however, only those with IBS report symptoms. This suggests that altered visceral sensitivity is the likely pathogenic mechanismMajor, 2017.

If food intolerance is clinically suspected, the only appropriate investigation is a trial of an exclusion diet (excluding food groups or components of food groups from the diet); see Exclusion diets to diagnose food intolerance.

If there is no clear benefit from initial dietary therapy, consider referral to an accredited practising dietitian with experience in managing IBS for trial of a low-FODMAP diet or consideration of food chemical sensitivity if symptoms are clinically suggestive of this.