A plate of grilled chicken over a quinoa salad with cucumber, pepper and orange

Irritable bowel syndrome

Low FODMAP Diet

The best-evidenced diet for IBS — and it is meant to be temporary.

Core restriction: Fermentable oligo-, di-, mono-saccharides and polyols
Difficulty: ●●●●●
Check a food: Open the food checker

A gentle reminder. This guide is for learning, not a prescription. Therapeutic diets interact with medication and conditions, so it's worth talking to your doctor or a registered dietitian before you begin.

Download this guide as a PDF Open the printable version

A tidy few pages with the food lists, meal plan and reminders — good for the fridge door or the first appointment with your dietitian.

How it works

FODMAPs are short-chain carbohydrates that are poorly absorbed in the small intestine. They draw water into the bowel osmotically, then get fermented rapidly by colonic bacteria into gas. In a sensitive gut, that distension is what produces pain and bloating.

Developed at Monash University, the diet runs in three phases: 2-6 weeks of restriction, then structured challenges of each FODMAP subgroup, then a personalised long-term diet that includes everything you tolerate.

Around 70% of people with IBS get meaningful symptom relief in the restriction phase. The phase that determines long-term quality of life, though, is reintroduction.

Nutrition at a glance

Low FODMAP is a three-phase diagnostic process, and phase one is the shortest part of it.

Phase 1 elimination: 2-6 weeks; Never longer without a dietitian
Phase 2 challenges: 6-8 weeks; One FODMAP group at a time, escalating doses
Phase 3: Personalised, long term; The widest diet your gut allows
Response rate: ~70% of IBS; One of the better-evidenced dietary therapies
Fibre: 25-30 g/day; Low FODMAP does not mean low fibre

Nutrients that often run short

Fibre
Calcium
Iron
Prebiotics
B vitamins

These are the ones worth planning for — through food where you can, and through a supplement your clinician suggests where you can't.

A word on electrolytes

Any change in how you eat changes how much sodium, potassium and magnesium you take in — usually downwards, because cooking from scratch removes the packaged foods that supplied most of it. Headaches, cramps, lightheadedness on standing and that flat, foggy feeling in the first fortnight are far more often an electrolyte dip than the diet failing. Drink to thirst rather than to a rule, salt your food unless you have been told not to, and lean on potassium- and magnesium-rich whole foods.

Sodium, potassium and magnesium are the three that matter most day to day. If you have kidney disease, heart failure or high blood pressure, or you take a diuretic, ACE inhibitor or ARB, set your targets with your clinician rather than with a supplement label — and avoid potassium-based salt substitutes unless you have been told they are safe for you.

Key cautions

None of this is meant to frighten you off. These are simply the things that most often catch people out on this diet — the ones worth raising at your next appointment.

Talk to a clinician
Get red flags investigated first
Weight loss, bleeding, anaemia, night symptoms or onset after 50 need investigation for coeliac disease, IBD and cancer before any IBS diet.
Worth testing
Test for coeliac before cutting wheat
Coeliac serology is unreliable once gluten is already out of the diet.
Keep an eye on
Phase one shrinks beneficial bacteria
Bifidobacteria fall measurably during elimination. That is acceptable for weeks and not for months.
Keep an eye on
Most people are not sensitive to everything
The usual result is two or three problem groups, with the rest returning freely. Skipping challenges keeps you needlessly restricted.

Used for

IBS — all subtypes
Functional bloating and abdominal distension
Symptom management in quiescent IBD
Adjunct in SIBO management
Endometriosis-associated bowel symptoms

What to eat

Eat freely

Vegetables

Carrot
Zucchini
Cucumber
Lettuce
Bell pepper
Green beans
Potato
Spinach
Tomato
Aubergine

Fruit

Strawberry
Blueberry
Kiwi
Orange
Grapes
Unripe banana
Cantaloupe
Pineapple

Protein

All plain meat, fish and eggs
Firm tofu
Tempeh

Grains and dairy

Rice
Oats
Quinoa
Gluten-free bread
Sourdough spelt
Lactose-free milk and yoghurt
Hard cheese

Eat with care

Portion determines everything

Avocado — an eighth is low FODMAP, a half is not
Sweet potato — half a cup only
Almonds — ten nuts
Broccoli heads yes, stalks no
Butternut squash, beetroot, savoy cabbage in measured portions

Best to skip

Fructans and GOS

Onion
Garlic
Wheat, rye and barley in quantity
Beans and lentils
Cashews and pistachios
Chicory root and inulin

Excess fructose

Apple
Pear
Mango
Watermelon
Honey
High-fructose corn syrup
Fruit juice

Lactose

Milk
Ice cream
Soft cheese
Regular yoghurt

Polyols

Stone fruit
Mushroom
Cauliflower
Sorbitol, mannitol, xylitol
Sugar-free gum and mints

Three days of meals

Day 1

Breakfast: Oats with lactose-free milk, strawberries, maple syrup.
Lunch: Chicken and rice bowl with carrot, cucumber and sesame-free dressing.
Dinner: Steak, roast potato, green beans, garlic-infused oil.
Snack: Ten almonds and a kiwi.

Day 2

Breakfast: Two eggs on sourdough spelt toast with spinach.
Lunch: Tuna salad with lettuce, tomato and pepper on gluten-free bread.
Dinner: Prawn stir fry with bok choy, carrot and rice noodles, ginger and spring onion greens.
Snack: Lactose-free yoghurt with blueberries.

Day 3

Breakfast: Smoothie with unripe banana, lactose-free milk and peanut butter.
Lunch: Rice paper rolls with chicken, cucumber and mint.
Dinner: Baked salmon, quinoa, roasted zucchini and aubergine.
Snack: Orange.

Getting started

1
Get an IBS diagnosis first. Coeliac disease, IBD and colon cancer can present the same way and need excluding.
2
Use the Monash app. Thresholds are portion-based and change with testing; printed lists go stale.
3
Restrict for two to six weeks only — never longer without reintroduction.
4
Use garlic-infused oil. Fructans are water-soluble, not oil-soluble, so the flavour transfers and the FODMAP does not.
5
Challenge each subgroup separately: fructose, lactose, fructans, GOS, sorbitol, mannitol.

Common mistakes

Living on the restriction phase indefinitely and shrinking your microbiome along with your food list.
Treating it as gluten-free. Wheat is a fructan problem here, not a gluten problem.
Ignoring portion size — most FODMAP foods are dose dependent.
Doing challenges while stressed, ill, or menstruating and getting uninterpretable results.
Forgetting the non-diet drivers: sleep, stress and gut-brain therapies work at least as well for many.

FAQs

How long is the restriction phase?

Two to six weeks. If there is no improvement in six weeks, FODMAPs are not your trigger and you should stop.

Can I eat gluten?

Yes, if you do not have coeliac disease. Sourdough spelt and small portions of wheat are often fine because the issue is fructan load.

Do I need a dietitian?

It roughly doubles success rates, mostly because reintroduction is where people go wrong on their own.

Stacking with other diets

Low FODMAP is the backbone of most SIBO diets.
Low FODMAP plus gluten-free is easy — most gluten-free grains are low FODMAP.
Low FODMAP plus low histamine is very restrictive; do them in sequence, not together.

See the full comparison table