Low FODMAP Diet: Phases, Foods & IBS Guide

If you’ve ever doubles over after a seemingly harmless meal, you’re not alone — roughly 1 in 10 adults deal with irritable bowel syndrome, and many spend years chasing down which foods are to blame. The low FODMAP diet offers a structured way to find out, using a three-phase approach that researchers at Monash University developed specifically to help people with IBS identify their personal triggers.

Developed by: Monash University · Primary use: IBS symptom management · Phases: 3-step process · Key restriction: Fermentable carbs · Top sources: NHS, Johns Hopkins

The table below summarizes key parameters for the Monash University-developed low FODMAP diet protocol.

What do you eat on a low FODMAP diet?

The key to eating low FODMAP isn’t about memorizing a long list of forbidden foods — it’s about swapping high FODMAP ingredients for alternatives that won’t ferment in your gut and cause symptoms like bloating, gas, or diarrhea. The Monash University FODMAP Diet App uses a traffic light system to make this easier, marking foods as green (low), yellow (moderate), or red (high) so you can see at a glance what fits your current phase.

Safe proteins

• Chicken, turkey, beef, pork, lamb — plain cooked portions
• Fish and seafood, including salmon, tuna, and shrimp
• Eggs in any preparation without high FODMAP add-ins
• Tofu (firm or extra-firm varieties), as documented in PMC peer-reviewed research

Low FODMAP vegetables

• Carrots, spinach, zucchini, kale, and bok choy
• Potatoes, sweet potatoes, and taro
• Peppers, cucumber, lettuce, and tomatoes
• Oyster mushrooms, bamboo shoots, and chives (as onion substitute)

Low FODMAP fruits

• Bananas, blueberries, strawberries, and oranges
• Grapes, kiwi, pineapple, and papaya
• Melons, cantaloupe, and honeydew
• Examples of low FODMAP swaps: apple for orange, as recommended by Monash FODMAP specialists

Grains and alternatives

• Rice, rice noodles, and rice-based products
• Gluten-free bread and pasta made from corn, quinoa, or potato
• Oats (plain, not flavored) — a standard low FODMAP breakfast includes oats with lactose-free milk and suitable fruit, per About IBS dietary guidelines
• Polenta, millet, and buckwheat

What foods can’t you eat on low FODMAP?

During Phase 1, you restrict foods that score red on the Monash app — essentially anything high in fermentable carbohydrates that your small intestine absorbs poorly. The goal is to give your gut a reset window, typically 2-6 weeks, before methodically testing which of these categories actually triggers your symptoms.

High FODMAP fruits and veggies

• Apples, pears, peaches, cherries, and mangoes
• Watermelon, , and canned fruit in syrup
• Onions, garlic, cauliflower, asparagus, and mushrooms
• Artichokes, Brussels sprouts, and legumes like lentils and chickpeas

Dairy and alternatives

• Regular milk, soft cheeses, yogurt, and ice cream
• Condensed milk and any dairy with lactose remaining
• Swap for lactose-free milk, hard cheeses, or dairy alternatives like oat milk (watch for added inulin)

Grains to avoid

• Wheat-based bread, pasta, and baked goods
• Rye and barley products
• Crackers or snacks made with high FODMAP flours

Other triggers

• Honey and high-fructose corn syrup
• Sugar alcohols like sorbitol and mannitol (common in sugar-free gum and candy)
• Legumes overall, including baked beans and kidney beans

What is the low FODMAP diet?

The low FODMAP diet is a substitution diet, not an elimination diet — you swap high FODMAP foods for low alternatives rather than cutting out entire food groups. Monash University researchers first published the approach in 2006, and it has since become one of the most studied dietary interventions for IBS, with clinical evidence supporting symptom improvement in roughly 70% of patients, per A Little Bit Yummy Monash Q&A.

FODMAP breakdown

• Fructose: Found in honey, some fruits, and high-fructose corn syrup
• Lactose: The sugar in dairy products
• Sorbitol & Mannitol: Sugar alcohols used as artificial sweeteners
• Fructans: Found in wheat, onions, garlic, and some vegetables
• Galactans (GOS): Found in legumes and some nuts

Who it’s for

The diet targets people with IBS who experience bloating, gas, constipation, diarrhea, or abdominal pain. It is not a general wellness diet — it is a therapeutic tool for a diagnosed condition. The Monash University protocol PDF explicitly notes it addresses gut symptoms like bloating and pain.

3 phases explained

Below is the three-phase structure Monash University developed for systematic FODMAP reintroduction.

During Phase 2, each challenge uses a food containing only one FODMAP group, with amounts increasing over 3 days, according to Monash FODMAP starting guidelines. The Monash App diary helps track symptoms throughout.

What to eat during an IBS flare-up?

An IBS flare-up can strike without warning, and what you eat in the first moments matters. During active symptoms, gentle, easy-to-digest foods that won’t add fermentable bulk are your best bet.

Diarrhea management foods

• Plain white rice or rice porridge
• Bananas (especially unripe for firming stool)
• Saltine crackers and plain toast
• Oral rehydration solutions or clear broths

Drinks for IBS mornings

Start with water at room temperature before adding anything else. Ginger tea or peppermint tea can help settle nausea. Avoid caffeine on an empty stomach during a flare, and skip fruit juices — even fresh-squeezed ones often contain high-fructose triggers.

Hydration tips

• Sip water consistently throughout the day rather than gulping
• Consider electrolyte drinks if diarrhea is persistent
• Avoid alcohol and carbonated beverages during active symptoms

What are common IBS triggers?

IBS triggers vary wildly from person to person, which is exactly why the low FODMAP approach works — it replaces guesswork with systematic testing. The six FODMAP groups each represent a different fermentable carbohydrate that may or may not affect you.

Number one trigger

There is no single universal IBS trigger, but fructose and fructans consistently show up as common offenders. Many people react strongly to foods containing both fructose and sorbitol, such as apples and pears, which Monash describes as optional Phase 2 challenge foods precisely because they affect so many people.

Bristol Stool Chart Type 7

Type 7 on the Bristol Stool Chart indicates severe diarrhea — loose, watery stools with no solid pieces. This often signals that fermentable foods are reaching the colon and drawing water in via osmosis, a process directly targeted by the low FODMAP mechanism. Bulking foods like white rice and bananas help counter this during acute phases.

Personalization after elimination

The Monash researchers emphasize that FODMAP tolerance can change over time, so re-challenging poorly tolerated foods every few months makes sense. Phase 3 uses the app’s filter function to help you expand your diet safely while staying symptom-free, per Monash FODMAP personalization guidance. For a simple and satisfying meal, consider these easy chicken and rice recipes easy chicken and rice recipes.

How to follow the low FODMAP diet step by step

Working through the three phases methodically gives you the best chance of identifying your specific triggers while maintaining nutritional balance. Here is how to approach each phase:

Prepare for Phase 1

1. Download the Monash FODMAP Diet App — it contains the most current food database with serving sizes
2. Stock your pantry with green-rated staples: rice, quinoa, lactose-free milk, hard cheese, and a variety of low FODMAP vegetables
3. Choose a low-stress 2-6 week window to start — dietary changes are harder to sustain during busy periods
4. Consider consulting a FODMAP-trained dietitian for personalized guidance through all phases, as recommended by A Little Bit Yummy Monash Q&A

Complete Phase 1: Elimination

1. Restrict all high FODMAP foods — stick exclusively to green servings per the Kaiser Permanente elimination phase guide
2. Track symptoms daily using the Monash App diary function
3. Expect symptom improvement within 2-6 weeks if FODMAPs are a significant trigger for you
4. Do not extend Phase 1 beyond 6 weeks without professional supervision

Work through Phase 2: Reintroduction

1. Test one FODMAP group at a time using 3-day food challenges, as detailed by Dr. Bojana’s reintroduction guide
2. Day 1: Small serving of the test food; Day 2: Moderate serving; Day 3: Normal serving
3. Record symptoms after each serving using the Monash App diary
4. Return to strict low FODMAP for 3 days between each challenge to clear your system
5. Complete all six groups before moving to Phase 3

Implement Phase 3: Personalization

1. Use your challenge results to build a long-term eating plan that includes all tolerated FODMAPs
2. Use the Monash App filter function to find recipes and products that fit your new profile
3. Re-test previously poorly tolerated groups every 3-6 months, as tolerance can shift over time, per Monash FODMAP research blog
4. Aim for the least restrictive diet possible while staying symptom-free

Monash University researchers

The low FODMAP diet is a learning journey that helps you identify what foods trigger your gut symptoms.

About IBS patient education platform

Phase 1 is not a forever diet; aim for minimal restriction long-term.