What low‑FODMAP (low fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet protocol is recommended for a patient with chronic abdominal pain, bloating, gas, diarrhea or constipation consistent with irritable bowel syndrome (IBS)?

Low-FODMAP Diet Protocol for IBS

The low-FODMAP diet should be implemented as a structured three-phase protocol: restriction (4-6 weeks), reintroduction (6-10 weeks), and personalization, with guidance from a registered dietitian with GI expertise. 1

Patient Selection Criteria

Good candidates for the low-FODMAP diet include patients who: 2

• Have insight into their meal-related GI symptoms
• Are motivated to make dietary changes
• Are willing to follow-up with healthcare providers

Poor candidates who should not attempt this diet include: 2

• Patients already consuming few culprit foods
• Those at risk for malnutrition or who are food insecure
• Patients with eating disorders or uncontrolled psychiatric disorders
• Individuals with moderate to severe anxiety or depression

Phase 1: Restriction Phase (4-6 Weeks)

Substantially reduce all FODMAP intake during this diagnostic phase to determine if symptoms are linked to FODMAP sensitivity. 1

Foods to Eliminate:

• Wheat products, pasta, breads, breakfast cereals 2
• Milk and dairy products 2
• Garlic and onions 2
• Apple and pear products 2
• Legumes 2

Key Implementation Points:

• Consider daily multivitamin supplementation 1
• Patients typically report symptom improvement within 2-6 weeks 1
• If symptoms have not improved within 6 weeks, discontinue FODMAP restriction and transition to another treatment option 1
• Only patients who respond proceed to the reintroduction phase 1

Phase 2: Reintroduction Phase (6-10 Weeks)

Continue FODMAP restriction while systematically challenging with foods containing single FODMAPs, consumed in increasing quantities over 3 days while recording symptom responses. 1

Reintroduction Protocol:

• Test one FODMAP category at a time 1
• Increase dose over 3 consecutive days 1
• Monitor and record symptom responses throughout 1
• Common trigger FODMAPs include fructans, mannitol, and galacto-oligosaccharides 1
• Wheat, milk, and garlic are common culprit foods 1

Phase 3: Personalization Phase

Use reintroduction data to liberalize the diet and develop an individualized long-term eating pattern. 1

• Up to 76% of IBS patients can liberalize their diet after completing reintroduction 1
• The diet should not be continued indefinitely in its strictest form due to potential negative impacts on beneficial gut bacteria, particularly bifidobacteria 2

Expected Efficacy

Approximately 70% of IBS patients respond to the low-FODMAP diet, with network meta-analyses demonstrating superiority over other dietary interventions. 2, 3

• In randomized trials, 62.7% achieved >50-point reduction in IBS Symptom Severity Score with low-FODMAP diet versus 40.8% with traditional dietary advice 1
• The diet ranks first for relief of global symptoms, abdominal pain, and bloating compared to all other dietary interventions 1, 3
• Long-term studies show sustained symptom relief with an adapted FODMAP approach in 50-60% of patients 2

Critical Role of Dietitian Support

Referral to a registered dietitian nutritionist with GI expertise is strongly recommended, as the diet is complex and potentially associated with increased food costs. 1, 2

• RDN support is crucial for executing the prescribed diet and optimizing outcomes 1
• When taught by an RDN, the diet may actually improve overall diet quality relative to habitual diets of most IBS patients 1

Important Caveats

• Ensure adequate fluid intake when increasing fiber, as insufficient fluids can cause constipation 2
• Monitor for nutritional deficiencies and overly restrictive eating habits during follow-up 2
• For patients with comorbid mental health conditions, consider a gentler "bottom-up" approach focusing on selected high-FODMAP foods rather than complete restriction 2
• Screen for eating disorders using the SCOFF questionnaire before initiating the diet 2