If you have IBS, chances are someone has mentioned the Low FODMAP diet. Your GP, a dietitian, a fellow sufferer in an online forum, or a label on a product that proudly declares itself FODMAP certified. But what does it actually mean — and does it work?
Here's everything you need to know to get started, written in plain English without the jargon.
What Does FODMAP Stand For?
FODMAP is an acronym developed by researchers at Monash University in Melbourne, Australia. It stands for:
F - ermentable
O - ligosaccharides (fructans and GOS — found in wheat, onion, garlic, legumes)
D - saccharides (lactose — found in milk, soft cheese, yoghurt)
M - onosaccharides (fructose — found in honey, apples, mangoes)
and
P - olyols (sorbitol and mannitol — found in stone fruits, some vegetables and artificial sweeteners)
These are all types of short-chain carbohydrates that are poorly absorbed in the small intestine. In people with IBS, they pass through to the large intestine where gut bacteria ferment them rapidly — producing gas, drawing water into the bowel and triggering the familiar symptoms of bloating, cramping, diarrhoea and constipation.
Who Developed the Low FODMAP Diet?
The Low FODMAP diet was developed by a team at Monash University led by Professor Peter Gibson and Dr Sue Shepherd. It emerged from research in the early 2000s investigating the link between diet and IBS symptoms and has since become the most widely studied and recommended dietary approach for IBS management in the world.
It is now recommended by the NHS, the British Dietetic Association and gastroenterology guidelines across Europe, North America and Australia.
Does It Actually Work?
Yes — and the evidence is unusually strong for a dietary intervention. Multiple randomised controlled trials have shown that the Low FODMAP diet reduces IBS symptoms in approximately **75% of people** who follow it correctly. That figure is significantly higher than most other dietary approaches to IBS and comparable to some medication-based treatments.
The key phrase is "who follow it correctly" — the diet has three distinct phases and skipping or shortcutting the process significantly reduces its effectiveness.
The Three Phases of the Low FODMAP Diet
Phase 1 — Elimination (2–6 weeks)
During this phase you remove all high FODMAP foods from your diet. This gives your gut a chance to settle and your symptoms to reduce. Most people start to notice improvement within 2–4 weeks.
This phase is not meant to be permanent. It is a diagnostic tool, not a long-term eating plan.
Phase 2 — Reintroduction (6–8 weeks)
One by one, you systematically reintroduce high FODMAP foods from each category to identify which specific FODMAPs trigger your symptoms. This is the most important phase and the one most people skip — which is a mistake.
Without reintroduction you don't know which foods are actually your triggers. You may be unnecessarily restricting foods that you can actually tolerate, which makes the diet harder to sustain and can affect nutritional balance.
Phase 3 — Personalisation (ongoing)
Based on what you learn in Phase 2, you build a personalised long-term eating pattern that avoids only your specific triggers. Most people find they can tolerate many FODMAP foods in normal quantities — it's usually a smaller subset that causes their particular symptoms.
What Can You Eat on a Low FODMAP Diet?
The list of low FODMAP foods is actually extensive. You are not restricted to a handful of bland options. Some of the foods that are Low FODMAP include:
Proteins: Eggs, chicken, beef, fish, firm tofu, tempeh, and — critically for vegans — certified Low FODMAP plant protein powders like That Protein.
Grains: Oats (in certified Low FODMAP quantities), rice, quinoa, gluten-free pasta, sourdough spelt bread (in small portions).
Vegetables: Carrots, courgette, cucumber, aubergine, green beans, kale, spinach, potato, sweet potato, tomato (in portions), bell peppers.
Fruit: Strawberries, blueberries, raspberries, oranges, grapes, kiwi, unripe banana, pineapple (in portions up to 140g).
Dairy alternatives: Almond milk (250ml), lactose-free milk, hard cheeses.
Fats and flavourings: Olive oil, garlic-infused oil, spring onion tops, chives, most herbs and spices, soy sauce (in small amounts), maple syrup (in small amounts).
The Protein Challenge for Vegans and Vegetarians
One of the most common difficulties people face on a Low FODMAP diet — particularly those eating plant-based — is getting adequate protein. Many of the most convenient plant protein sources are high FODMAP:
Legumes (beans, lentils, chickpeas) — high in GOS
Cashews and pistachios — high in GOS and fructans
Most protein powders — contain inulin, chicory root, artificial sweeteners or other high FODMAP additives
That Protein exists specifically to solve this problem. It's the UK's only independently laboratory-tested and certified Low FODMAP vegan protein powder. Made with organic plant ingredients, no artificial additives and no hidden FODMAP triggers — it's designed for people who need reliable plant protein without the digestive consequences.
Do You Need to See a Dietitian?
Yes — ideally. The Low FODMAP diet is complex enough that doing it without professional guidance significantly increases the risk of making mistakes, missing your actual triggers, or unnecessarily restricting your diet long-term. The British Dietetic Association and Monash University both recommend working with a registered dietitian trained in the Low FODMAP diet.
Your GP can refer you, or you can find a FODMAP-trained dietitian through the British Dietetic Association's Find a Dietitian tool.
Getting Started: Practical First Steps
1. See your GP first — get a formal IBS diagnosis before changing your diet significantly
2. Find a FODMAP-trained dietitian — ideally work with a professional through the process
3. Download the Monash University FODMAP app — the most accurate and up-to-date FODMAP database available
4.Clear your kitchen of high FODMAP staples — onion, garlic, wheat products, regular milk
5. Stock up on Low FODMAP basics — oats, rice, almond milk, eggs, fresh herbs, that Protein
6.Give it time — most people need 2–4 weeks to see meaningful symptom improvement
Explore That Protein's Certified Low FODMAP Range
Everything in the That Protein range is made without artificial flavours, sweeteners or additives — and our flagship products carry full FODMAP Friendly certification. Browse the full range at [thatprotein.com](https://www.thatprotein.com/blogs/news/low-fodmap) with free UK delivery on orders over £40.
*Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult your GP or a registered dietitian before beginning an elimination diet.*