Low-FODMAP Diet for IBS — Foods List and Guide
The low-FODMAP diet is the most evidence-based dietary approach for managing irritable bowel syndrome (IBS). It was developed by researchers at Monash University in Australia and has been validated in multiple clinical trials. The diet targets short-chain carbohydrates that are poorly absorbed in the small intestine, fermented rapidly by gut bacteria, and osmotically active — all of which can trigger IBS symptoms in sensitive individuals.
What Are FODMAPs?
FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. These are short-chain carbohydrates and sugar alcohols that resist digestion in the small intestine, pass into the large bowel, and are rapidly fermented by bacteria. In people with IBS, this process generates excess gas, alters fluid balance in the gut, and triggers symptoms including bloating, abdominal pain, diarrhea, and constipation. The five FODMAP categories are: fructans (found in garlic, onion, wheat), galacto-oligosaccharides or GOS (found in legumes), lactose (found in dairy), excess fructose (found in apples, honey, high-fructose corn syrup), and polyols (found in stone fruits, cauliflower, and artificial sweeteners ending in '-ol'). The Monash University FODMAP Diet was first published in 2005 and is now endorsed by major gastroenterological societies worldwide, including the British Dietetic Association and Gastroenterological Society of Australia. It is a structured three-phase protocol — not a permanent diet — designed to identify individual food triggers and restore the widest possible diet long-term.
Low-FODMAP Foods (Safe During Elimination)
These foods have been laboratory-tested by Monash University and confirmed low in FODMAPs at the serving sizes listed. They are generally safe to eat freely during the 2–6 week elimination phase. Serving size matters — larger portions of some foods can shift them into the high-FODMAP range.
| Food | Category | Safe Serving Size |
|---|---|---|
| White rice, cooked | Grain | 1 cup (180 g) |
| Gluten-free rolled oats | Grain | ½ cup dry (52 g) |
| Sourdough spelt bread | Grain | 2 slices (109 g) |
| Chicken breast, cooked | Protein | Any portion |
| Eggs | Protein | 2 large |
| Firm tofu | Protein | ⅔ cup (170 g) |
| Canned chickpeas, rinsed | Protein / Legume | ¼ cup (42 g) |
| Blueberries | Fruit | 1 cup (125 g) |
| Oranges | Fruit | 1 medium (130 g) |
| Strawberries | Fruit | 10 medium (150 g) |
| Unripe banana | Fruit | 1 medium (100 g) |
| Carrots, raw | Vegetable | 1 medium (61 g) |
| Potato, boiled | Vegetable | 1 medium (150 g) |
| Zucchini | Vegetable | ½ cup chopped (65 g) |
| Spinach, raw | Vegetable | 1 cup (30 g) |
| Lactose-free milk | Dairy | 1 cup (250 mL) |
| Hard cheese (cheddar, parmesan) | Dairy | 40 g |
High-FODMAP Foods to Avoid During Elimination
These foods are high in one or more FODMAP types and should be avoided during the elimination phase. This is not a permanent list — the reintroduction phase is designed to test which of these you personally tolerate.
| Food | FODMAP Type | Why It Triggers Symptoms |
|---|---|---|
| Garlic | Fructans | Very high fructan content even in small amounts; garlic powder is equally high |
| Onion (all varieties) | Fructans | One of the most common IBS triggers; fructans survive cooking |
| Wheat bread, pasta, cereals | Fructans | Fructans in wheat are distinct from gluten; low-gluten is not the same as low-FODMAP |
| Apple | Excess fructose | Contains more fructose than glucose, which impairs absorption in the small intestine |
| Mango | Excess fructose | High free fructose; ripe mangoes are particularly concentrated |
| Regular cow's milk | Lactose | Lactose is a disaccharide requiring lactase; many IBS patients have reduced lactase |
| Soft cheese (ricotta, cottage) | Lactose | High residual lactose compared to aged hard cheeses |
| Cauliflower | Polyols (mannitol) | Among the highest mannitol vegetables; ½ cup is enough to trigger symptoms in sensitive individuals |
| Mushrooms | Polyols (mannitol) | Mannitol content increases with common cultivated varieties; canned mushrooms are similarly high |
| Dried lentils, kidney beans | GOS (galacto-oligosaccharides) | Canned and rinsed versions are lower — rinsing removes surface oligosaccharides |
| Watermelon | Polyols (mannitol) + excess fructose | Double FODMAP source; even small portions can be problematic |
| Honey | Excess fructose | Fructose-to-glucose ratio is very high; maple syrup is a lower-FODMAP alternative |
| Cashews, pistachios | Fructans + GOS | High in multiple FODMAP types; most other nuts (macadamia, walnuts) are low-FODMAP |
The Three Phases Explained
The low-FODMAP diet is a structured temporary protocol with three distinct phases. Skipping phases or using the elimination phase as a long-term diet is a common and clinically problematic error. **Phase 1 — Elimination (2–6 weeks):** All high-FODMAP foods are replaced with low-FODMAP alternatives. The goal is symptom relief, not permanent restriction. Most people with IBS experience meaningful improvement within two to four weeks. If there is no improvement after six weeks, other diagnoses should be considered with your doctor — the low-FODMAP diet does not work for everyone. **Phase 2 — Reintroduction (6–8 weeks):** One FODMAP group is reintroduced at a time using a standardized challenge protocol. For example, lactose is tested with regular milk over three days while the rest of the diet stays low-FODMAP. This phase identifies which specific FODMAP types — not foods — trigger your symptoms. Reintroduction is the most important phase because it moves the diet from restriction to precision. **Phase 3 — Personalization (long-term):** Based on reintroduction results, a personalized diet is established that avoids only the FODMAP types that caused symptoms, in amounts that reliably triggered reactions. Most people can reintroduce the majority of high-FODMAP foods at some level. The goal is the least restrictive diet that keeps symptoms controlled.
Important Warnings
- The low-FODMAP diet is not a lifelong diet. Using the elimination phase permanently without completing reintroduction leads to unnecessary nutritional restriction and reduced gut microbiome diversity.
- This diet requires guidance from an accredited dietitian trained in the Monash FODMAP protocol. Unsupervised attempts frequently result in inadequate nutrition, incomplete reintroduction, or failure to identify the actual trigger foods.
- The low-FODMAP diet is not appropriate for everyone. It should not be used by people with eating disorder history, during pregnancy, or in children without specialist supervision.
- Long-term elimination of high-FODMAP foods reduces prebiotic intake, which negatively affects beneficial gut bacteria. Research from King's College London shows this effect reverses once personalization is complete.
- Serving size is critical. Many foods are low-FODMAP at one serving and high-FODMAP at double the serving. The Monash University FODMAP app is the most current and validated reference for specific portion thresholds.
- The low-FODMAP diet treats IBS symptoms — it does not treat the underlying cause. If you have not received a formal IBS diagnosis, see a gastroenterologist first. Symptoms overlapping with IBS can indicate inflammatory bowel disease, celiac disease, or colorectal cancer.
- FODMAPs are not harmful to people without IBS. Do not adopt this diet unless you have a confirmed IBS diagnosis and a clinical reason to try it.
Sources
Note: This page provides general nutrition education about the low-FODMAP diet. It is not medical advice and does not replace a clinical assessment. IBS management requires a confirmed diagnosis and personalized guidance from a gastroenterologist and accredited dietitian trained in the FODMAP protocol. Do not begin this diet based on this page alone. Full disclaimer.