The Low FODMAP diet is the most evidence-based dietary intervention for IBS, with clinical studies showing symptom improvement in up to 86% of patients. But starting it can feel overwhelming. This guide covers everything you need to know to begin confidently.
What Are FODMAPs?
FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. These are short-chain carbohydrates that are poorly absorbed in the small intestine. When they reach the large intestine, gut bacteria ferment them — producing gas, drawing in water and triggering the bloating, cramping, urgency and pain that define IBS.
The Three Phases
Phase 1 — Elimination (2-6 weeks): Remove all high FODMAP foods. This is a diagnostic tool, not a permanent diet.
Phase 2 — Reintroduction (6-8 weeks): Systematically reintroduce FODMAP groups one at a time to identify your personal triggers.
Phase 3 — Personalisation (ongoing): Build a long-term diet based on your individual tolerances.
High FODMAP Foods to Avoid in Phase 1
- Wheat, rye and barley
- Onion and garlic — the two most common triggers
- Apples, pears, watermelon and mango in large quantities
- Cow's milk, soft cheese and yogurt
- Legumes — lentils, chickpeas, kidney beans
- Sweeteners ending in -ol (sorbitol, xylitol, mannitol)
Low FODMAP Foods You Can Eat Freely
- Rice, oats, quinoa, gluten-free pasta
- Eggs, firm tofu, tempeh
- Oat milk, lactose-free dairy
- Carrots, courgette, spinach, cucumber, tomatoes
- Strawberries, blueberries, kiwi, oranges
- Brown rice protein powder (certified Low FODMAP)
Protein on the Low FODMAP Diet
Getting enough protein is one of the biggest challenges. See our complete guide to the best vegan protein sources for IBS and our breakdown of how to read a protein powder label to avoid hidden FODMAP triggers.
Shopping for Low FODMAP in UK Supermarkets
See our complete UK supermarket shopping guide for exactly what to buy and what to avoid.