If everything you eat seems to upset your stomach, you're not imagining it – in gut-brain disorders, such as IBS, dyspepsia, and functional constipation, the problem is usually a sensitive gut-brain system, not the food itself.
Even though it might feel like every food is a problem, intolerances aren't always the full explanation. What's actually happening is that the gut is more reactive than it should be – which is why foods that most people tolerate easily can still trigger bloating, pain, and urgency.
This means food may be the trigger, but it is not the root cause – the underlying issue is heightened gut-brain sensitivity.
Why does food upset my stomach?
Every time you eat, your digestive system activates – your stomach stretches, acid is released, your intestines contract, and digestion naturally produces some gas.
Some foods increase this activity more than others. Foods high in FODMAPs – such as onions, apples, wheat, and certain dairy products – are fermented in the gut and produce more gas and pressure.
For most people, that pressure is barely noticeable. But in gut-brain disorders like IBS, the same pressure can feel painful or urgent – not because something is wrong with the food, but because the gut's nerves are more sensitive than they should be.
This is why the low FODMAP diet can reduce symptoms for some people – by lowering fermentation and gas production, there's less pressure for a sensitive gut to react to. But it doesn't change the underlying sensitivity itself.
That heightened response to normal digestive signals is known as visceral hypersensitivity.
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Why is eating painful even when my tests are normal?
Visceral hypersensitivity is increased sensitivity of the nerves in the digestive tract – meaning normal digestion can feel painful or uncomfortable. It is a core feature of gut-brain disorders like IBS, even when blood tests, scans, colonoscopy, and endoscopy all come back normal.¹
For most people, stomach stretching or mild gas is barely noticeable. In someone with a gut-brain disorder, those same sensations can feel intense and distressing. This isn't structural damage – it's altered signalling between the gut and the brain.
That distinction matters. It explains why cutting out food after food rarely resolves symptoms – and why so many people spend years feeling dismissed before getting a diagnosis that finally makes sense of their experience.
Even in overlapping conditions like GERD (Gastroesophageal Reflux Disease) and IBD (Inflammatory Bowel Disease), where inflammation or acid exposure may be present, gut-brain sensitivity can magnify how symptoms are experienced. That is why symptom severity doesn't always match what appears on testing.
Is it food intolerance or something else? How gut-brain disorders are different
Unlike true food allergies or celiac disease, which involve immune reactions or tissue damage, gut-brain disorders cause no structural injury – the problem is a nervous system that responds to food more sensitively than it should.
These conditions are formally recognized by gastroenterologists worldwide as disorders of gut-brain interaction under the Rome IV criteria² – diagnosed not by what shows up on tests, but by the pattern and history of symptoms.
Neurogastroenterologist Dr Justin Brandler describes these criteria as "clinical guardrails" that help determine whether what someone is experiencing reflects a gut-brain disorder – not a problem with the food they're eating.³
This is why strict elimination diets often provide only partial relief. Remove one suspected trigger and another takes its place – because the underlying sensitivity remains, regardless of what's on the plate.
What actually helps if food keeps upsetting my stomach?
Long-term improvement usually involves addressing both food triggers and nervous system regulation. Evidence-based dietary strategies combined with therapies that calm the gut-brain system – such as gut-directed hypnotherapy and stress-modulation techniques – can help reduce symptom amplification.
If you're also dealing with pain, the IBS Pain Guide covers the causes, locations, and relief strategies in depth.
If you live with a gut-brain disorder, your symptoms are real – and so are your food reactions. But your digestive system isn't damaged – it's sensitive. Understanding that distinction can help you move beyond fear-based dieting toward a more sustainable path to relief.
Watch: Dr Simone Peters of Monash University explains how gut-directed hypnotherapy compares to the low FODMAP diet in this short overview.
Frequently asked questions
Why does everything I eat seem to upset my stomach?
Usually it's not the food – it's a sensitive gut-brain system. In gut-brain disorders like IBS, dyspepsia, and functional constipation, the gut's nerves are more reactive than they should be, which is why foods that most people tolerate easily can still trigger real bloating, pain, and urgency.
Is it food intolerance or a gut-brain disorder?
It could be both, but they're different things. True food intolerances involve a reaction to a specific food. Gut-brain disorders cause widespread food sensitivity because the nervous system responds to normal digestion more intensely than it should – not because of immune reaction or tissue damage.
Why doesn't cutting out foods fix my symptoms?
Because elimination diets reduce fermentation and gas but don't change the underlying nerve sensitivity. This is why removing one trigger often leads to reacting to another – the root cause is a reactive gut-brain system, not any individual food.
What is visceral hypersensitivity?
Visceral hypersensitivity is increased sensitivity of the nerves in the digestive tract, making normal digestive activity – stretching, gas, and acid – feel more intense or painful than it should. It is a core feature of gut-brain disorders and explains why symptoms can be severe even when all tests come back normal.
Can food sensitivity in gut-brain disorders improve?
Yes. The most effective approach addresses both dietary triggers and nervous system regulation together. Therapies that calm gut-brain signaling, combined with evidence-based dietary strategies, can significantly reduce how reactive the gut is to food – without relying on permanent elimination diets.
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