What are the phases and guidelines for a low FODMAP (Fermentable Oligo-, Di-, Mono-saccharides, and Polyols) diet?

Low FODMAP Diet Chart and Implementation Guide

The low FODMAP diet is a structured three-phase intervention consisting of: (1) restriction phase lasting 4-6 weeks, (2) reintroduction phase lasting 6-10 weeks, and (3) personalization phase based on individual tolerance. 1, 2

Phase 1: Restriction (4-6 Weeks Maximum)

During this initial phase, substantially reduce intake of all high FODMAP foods while maintaining nutritional adequacy. 1, 2

Foods to Avoid (High FODMAP):

• Oligosaccharides (Fructans & GOS): Wheat, rye, onions, garlic, legumes/pulses 2, 3
• Disaccharides (Lactose): Milk, yogurt, soft cheeses 2
• Monosaccharides (Excess Fructose): Honey, apples, pears, high-fructose corn syrup 2
• Polyols (Sorbitol & Mannitol): Stone fruits, mushrooms, artificial sweeteners 2

Foods to Include (Low FODMAP):

• Proteins: Meat, fish, eggs, firm tofu 2
• Grains: Rice, oats, quinoa, gluten-free products 2
• Vegetables: Carrots, zucchini, bell peppers, spinach, potatoes 2
• Fruits: Bananas, blueberries, strawberries, oranges 2
• Dairy alternatives: Lactose-free milk, almond milk, hard cheeses 2

Key Implementation Points:

• Consider daily multivitamin supplementation during restriction 2
• Start with low doses of soluble fiber (3-4g daily) if needed, building to 20-30g/day to avoid exacerbating bloating 1, 4
• Patients typically report symptom improvement within 2-6 weeks 2
• If no improvement occurs within 4-6 weeks, abandon the diet and pursue alternative treatments 1, 3

Phase 2: Reintroduction (6-10 Weeks)

Systematically challenge with foods containing single FODMAPs while maintaining baseline restriction of all other FODMAPs. 2, 3

Reintroduction Protocol:

• Introduce one FODMAP group at a time in isolation 2, 3
• Test foods in increasing quantities over 3 consecutive days while monitoring symptoms 2
• Allow 3-day washout period between different FODMAP challenges 2
• Document symptom responses in a food diary 2

Common Trigger FODMAPs (in order of frequency):

1. Fructans (wheat, onion, garlic) 2, 3
2. Mannitol (mushrooms, cauliflower) 2, 3
3. Galacto-oligosaccharides (GOS) (legumes, pulses) 2, 3
4. Lactose (milk products) 2
5. Excess fructose 2
6. Sorbitol 2

Phase 3: Personalization (Long-Term)

Develop an individualized long-term diet based on reintroduction results, reincorporating tolerated FODMAPs to the maximum extent possible. 1, 3

• Reintroduce all tolerated FODMAPs to avoid unnecessary restriction 1, 3
• Do not continue strict FODMAP restriction indefinitely due to potential negative impacts on gut microbiome (particularly reduced bifidobacteria) and risk of nutritional deficiencies 1, 3
• Long-term studies show sustained symptom relief in 50-60% of patients with an adapted FODMAP approach 1, 3

Patient Selection Criteria

Good Candidates:

• Patients with insight into meal-related gastrointestinal symptoms 1, 2
• Motivated individuals willing to make dietary changes 1, 2
• Those willing to work with healthcare providers for follow-up 2
• Patients with moderate to severe gastrointestinal symptoms 3

Poor Candidates (Screen Out Before Starting):

• Patients consuming few culprit foods 1, 2
• Those at risk for malnutrition or who are food insecure 1, 2
• Individuals with eating disorders or uncontrolled psychiatric disorders 1, 2
• Patients with moderate to severe anxiety or depression 2, 3
• Screen using simple eating disorder questionnaires (e.g., SCOFF) before initiating the diet 1, 4

Professional Support Requirements

Referral to a registered dietitian nutritionist (RDN) with gastrointestinal expertise is strongly recommended, as the diet is complex and requires close monitoring. 1, 2, 3

• RDN support is crucial for optimizing outcomes and preventing nutritional deficiencies 1, 2
• If a gastrointestinal RDN is unavailable, other resources (apps, webinars) can assist, though they remove the personalized approach 1, 5
• The diet can be complex and potentially associated with increased food costs 2, 3

Expected Outcomes

• Approximately 70% of patients respond to the low FODMAP diet 2
• The diet demonstrates significant improvement in IBS Symptom Severity Score and quality of life 2
• Greater improvement in bloating compared to other dietary approaches 2
• Network meta-analyses show the low FODMAP diet is superior to other dietary interventions for reducing abdominal pain, bloating, and improving satisfaction with bowel habits 3

Critical Pitfalls to Avoid

• Never continue the strict restriction phase beyond 4-6 weeks 1, 3
• Do not skip the reintroduction phase, as this leads to unnecessary long-term restriction 1, 3
• Avoid implementing the diet without screening for eating disorders first 1, 4
• Do not use the diet as first-line therapy; try traditional dietary advice and soluble fiber first 1, 3
• For patients with psychological comorbidities, consider a gentler "bottom-up" approach focusing on selected high-FODMAP foods rather than complete restriction 2, 3

Alternative First-Line Approaches

Before attempting the low FODMAP diet, implement these strategies: 1, 3

• Regular meal patterns with adequate hydration 3, 4
• Limiting alcohol and caffeine 3, 4
• Reducing fatty and spicy foods 3, 4
• Soluble fiber supplementation (ispaghula) is efficacious for global IBS symptoms, particularly in constipation-predominant IBS 1, 3