What are FODMAPs?
FODMAP is an acronym created by researchers at Monash University (2005) standing 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, bacteria ferment them, rapidly producing gas and drawing in water.
| Group | Sources | Mechanism of Action |
|---|---|---|
| Oligosaccharides (Fructans & GOS) | Wheat, rye, onions, garlic, legumes, lentils. | Humans lack the enzymes to break these down completely; they are fermented by gut flora. |
| Disaccharides (Lactose) | Milk, soft cheeses, yogurt. | Requires the lactase enzyme, which many adults lack (lactase non-persistence). |
| Monosaccharides (Fructose) | Apples, pears, honey, high-fructose corn syrup. | Absorbed via slow capacity transporters; requires glucose to assist absorption. |
| Polyols (Sorbitol, Mannitol) | Apples, apricots, cauliflower, sugar-free gum. | Sugar alcohols that pull water into the intestines (osmotic effect), causing laxation. |
The Three Phases of the Protocol
The Low FODMAP diet is not a lifetime diet. Long-term restriction of these carbohydrates severely damages the diversity of the gut microbiome, specifically lowering beneficial Bifidobacteria levels (Staudacher et al., 2012).
1. Elimination
Duration: 2-6 weeks.
Strictly replace high FODMAP foods with low FODMAP alternatives to establish symptom control.
2. Reintroduction
Duration: 8-12 weeks.
Systematically challenge one FODMAP group at a time over 3 days (increasing doses) to identify specific triggers.
3. Personalization
Duration: Long-term.
Return to a normal diet, restricting only the specific FODMAPs identified in phase 2 at their threshold levels.
Phase 1: Elimination Guidelines
During the elimination phase, you must keep your total FODMAP load very low. However, portion size is critical. A food is rarely "zero" FODMAP; it is low FODMAP at a specific serving size.
The Concept of "Stacking"
Eating several different "low FODMAP" foods in one meal can cumulatively push your total intake over the threshold, triggering symptoms. This is known as FODMAP stacking.
Use our Stacking CalculatorCommon Pitfalls to Avoid
- Onion and Garlic Powders: These are highly concentrated fructans hiding in almost all savory processed foods and broths.
- Gluten-Free vs. Low FODMAP: Gluten is a protein, not a carbohydrate. While wheat contains fructans (FODMAP), not all gluten-free products are low FODMAP (many use high-FODMAP flours like amaranth or add inulin for fiber).
- Inulin / Chicory Root: A highly fermentable fiber often added to "health" foods, yogurts, and protein bars. It is a concentrated fructan.
Phase 2: Structured Reintroduction
Do not start reintroduction until your symptoms have significantly improved (usually defined as at least 3-4 days of consecutive relief). Test only one pure FODMAP source at a time.
| FODMAP Group | Standard Test Food | Day 1 Dose | Day 2 Dose | Day 3 Dose |
|---|---|---|---|---|
| Fructans (Wheat) | White bread (wheat) | 1 slice | 1.5 slices | 2 slices |
| Fructans (Onion) | Red onion | 1/8 onion | 1/4 onion | 1/2 onion |
| Fructose | Honey | 1 tsp | 2 tsp | 1 tbsp |
*Wait 2-3 washout days between testing different groups, or longer if symptoms were triggered.