Starting a Low FODMAP diet can feel overwhelming. The list of foods to avoid seems endless, the science is complicated, and working out what you can actually eat — let alone enjoy — takes time and research most people don't have.
So we've simplified it. Here are the five most common high FODMAP foods that trigger IBS symptoms, exactly why they cause problems, and the delicious gut friendly swaps that mean you don't have to feel deprived.
What Is a High FODMAP Food?
FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are short-chain carbohydrates that are poorly absorbed in the small intestine. Instead of being digested normally, they pass through to the large intestine where gut bacteria ferment them rapidly — producing gas, bloating, cramping, diarrhoea and constipation.
Not everyone reacts to the same FODMAPs in the same way or at the same quantities. But for people with IBS, reducing overall FODMAP load consistently reduces symptoms. Research from Monash University — the team who developed the Low FODMAP diet — shows that around 75% of IBS sufferers experience significant improvement following a Low FODMAP approach.
The 5 Foods Most Likely to Trigger Your IBS
1. Wheat and Gluten-Containing Grains
Wheat is one of the most significant FODMAP triggers for people with IBS — not because of the gluten itself, but because of the fructans it contains. Fructans are a type of oligosaccharide that ferments rapidly in the gut, causing gas and bloating even in people who don't have coeliac disease.
Common sources of wheat that catch people out: bread, pasta, couscous, flour-based sauces, cereals, crackers, pastry and most baked goods.
Low FODMAP swap: Oats (in certified Low FODMAP quantities), rice, rice pasta, quinoa, gluten-free bread made without high FODMAP ingredients. That Protein's porridge range is made with oats and is certified Low FODMAP — a safe, genuinely delicious wheat-free breakfast option.
2. Onion and Garlic
This one surprises people — and causes real frustration because onion and garlic are in almost everything. Both are extremely high in fructans and are among the most potent IBS triggers identified in FODMAP research. Even small amounts — cooked into a sauce, used as a base, or present as a powder — can be enough to trigger significant symptoms in sensitive individuals.
Garlic powder and onion powder are particularly problematic because they're concentrated and hidden in spice blends, stock cubes, ready meals, restaurant sauces and packaged foods.
Low FODMAP swap: Garlic-infused oil (the fructans don't transfer into oil, so the flavour is safe), spring onion green tops only (the white parts are high FODMAP), chives and fresh herbs for flavour.
3. Dairy — Milk, Soft Cheese and Yoghurt
The issue with dairy on a Low FODMAP diet is lactose — a disaccharide that many people struggle to digest properly. Lactose intolerance and IBS frequently overlap. When lactose isn't broken down in the small intestine, it passes to the large intestine where it ferments and causes the familiar symptoms of bloating, cramping and urgency.
Not all dairy is equally high in lactose. Hard cheeses like cheddar and parmesan are actually low in lactose and generally well tolerated. Milk, soft cheese, cream cheese, ice cream and most yoghurts are the main culprits.
Low FODMAP swap: Lactose-free milk, almond milk (in 250ml portions), oat milk (in 30ml portions), hard cheeses, lactose-free yoghurt. For protein, That Protein's plant-based powders are completely dairy-free, certified Low FODMAP and contain no lactose whatsoever.
4. Apples, Pears and Stone Fruits
Fruit is healthy — but some fruits are very high in fructose (a monosaccharide) and polyols, both of which are significant FODMAP triggers. Apples, pears, mangoes, watermelon, cherries, peaches, plums and nectarines are all high FODMAP and can cause significant digestive distress even in relatively small portions.
This doesn't mean avoiding all fruit. The key is choosing low FODMAP fruits and paying attention to portion size, since even low FODMAP fruits can become triggering in large amounts.
Low FODMAP swap: Strawberries, blueberries, raspberries, oranges, grapes, kiwi, pineapple (in portions up to 140g), unripe banana (ripe bananas are higher in fructose). Frozen berries are a particularly convenient option for smoothies and porridge.
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5. Legumes and Most Pulses
Beans, lentils and chickpeas are celebrated as plant protein powerhouses — and they are genuinely nutritious. But they're also very high in galacto-oligosaccharides (GOS), a type of oligosaccharide that ferments vigorously in the gut. For people with IBS, a portion of chickpeas or a bean-heavy meal can cause significant bloating and pain.
Canned legumes that have been rinsed thoroughly are somewhat lower in FODMAPs than dried and cooked from scratch, as some of the GOS leaches into the liquid during canning. But they're still high enough to cause problems in typical serving sizes.
Low FODMAP swap: Firm tofu and tempeh (which have lower FODMAP levels), canned lentils rinsed well in small portions (up to 46g), edamame in small portions. For protein specifically, rice protein and pea protein powders that have been independently certified as Low FODMAP are a much more reliable source of plant protein for people with IBS than whole legumes.
The Protein Problem on a Low FODMAP Diet
One of the most common challenges people face when starting a Low FODMAP diet is getting enough protein — especially on a plant-based diet. Many of the most convenient plant protein sources (legumes, certain grains, many protein powders) are either high FODMAP themselves or contain hidden high FODMAP additives like inulin, chicory root or artificial sweeteners.
That Protein was developed specifically to solve this problem. It's the UK's only certified Low FODMAP vegan protein powder — independently laboratory tested, additive-free and made with organic plant ingredients. No hidden triggers. No artificial sweeteners. Just clean plant protein that's safe for sensitive stomachs.
A Note on FODMAP Thresholds
One important point that's often missed: FODMAPs are dose-dependent. A food that's high FODMAP in a large serving may be perfectly safe in a small serving. This is why working with a registered dietitian trained in the Low FODMAP diet is strongly recommended, especially during the elimination phase. The goal isn't to avoid every FODMAP food forever — it's to identify your specific triggers through a structured elimination and reintroduction process.
Ready to Make Low FODMAP Eating Easier?
Browse That Protein's full certified Low FODMAP range at [thatprotein.com](https://www.thatprotein.com/collections/all-products) — free UK delivery on orders over £40.
*Disclaimer: This article is for informational purposes only and does not constitute medical advice. If you have IBS or any digestive condition, please consult your GP or a registered dietitian before making significant dietary changes.*