The low FODMAP diet is one of the most effective tools for managing IBS — but it's also easy to get wrong. Most of the frustration people feel comes down to a handful of avoidable mistakes. Here are the ten we see most often, and how to sidestep them.
1. Skipping the reintroduction phase
Elimination is only step one. The reintroduction phase is where you actually learn your triggers. Skip it and you stay needlessly restricted forever.
2. Staying in elimination too long
The strict phase is meant to last 2–6 weeks, not months. Long-term over-restriction can affect your nutrition and your gut bacteria.
3. Missing hidden onion and garlic
They hide in stocks, sauces, marinades and spice blends. Garlic-infused oil is a low FODMAP way to keep the flavour without the fructans.
4. Not using the Monash app
FODMAP levels are portion-dependent and updated regularly. The Monash University FODMAP app is the most accurate source for current serving sizes.
5. Going it alone
The diet is complex enough that a FODMAP-trained dietitian makes a real difference. Your GP can refer you, or you can find one via the British Dietetic Association.
6. Assuming gluten-free means low FODMAP
They're not the same thing. The issue with wheat is fructans, not gluten — and plenty of gluten-free products still contain high FODMAP ingredients.
7. Ignoring portion sizes
Many foods are low FODMAP in small servings and high FODMAP in large ones. Stacking several "low" portions in one meal can still tip you over.
8. Trusting "gut friendly" labels
"Gut friendly" is marketing, not a standard. Look for genuine independent certification. That Protein is the UK's only certified low FODMAP vegan protein — our Blissful Brown Rice & Raw Cacao is FODMAP Friendly certified, not just self-declared.
9. Overlooking protein and nutrition
Cutting out legumes and many staples can leave gaps — especially protein on a plant-based diet. A certified low FODMAP protein powder is an easy way to fill them.
10. Expecting overnight results
Most people need 2–4 weeks to see a meaningful change. Give it time and keep a symptom diary so you can actually see the progress.
Start on the right foot
Our beginner's guide to the low FODMAP diet walks through the three phases, and our shopping list makes the first food shop easy.
Browse the full range at thatprotein.com — free UK delivery on orders over £30.
This article is for general information and isn't medical advice. If you have IBS or any digestive condition, please consult your GP or a registered dietitian.