Irritable bowel syndrome (IBS) affects around 10-15% of the UK population, according to the NHS. It is a long-term condition that causes episodes of stomach cramps, bloating, diarrhoea, and constipation — often triggered or worsened by certain foods. While there is no single "IBS diet" that works for everyone, understanding which foods commonly cause flare-ups is a valuable first step towards feeling more in control.
IBS is not one-size-fits-all. The condition is classified into three main subtypes, and the foods that trigger symptoms can differ depending on which type you have.
A food that calms one subtype may worsen another. For instance, increasing fibre can help IBS-C but may aggravate IBS-D. This is why personalised tracking is so important — it helps you understand your specific pattern rather than following generic advice.
The table below lists foods that are most frequently reported as IBS triggers in the UK, along with the subtype they are most likely to affect and the mechanism behind the reaction.
| Food | Why It Triggers IBS | Subtype Most Affected |
|---|---|---|
| Onions & garlic | High in fructans (FODMAPs) that ferment in the gut, producing gas and drawing water into the bowel | All subtypes |
| Wheat bread & pasta | Fructan content causes fermentation; gluten sensitivity may also play a role in some individuals | All subtypes |
| Beans, chickpeas & lentils | Rich in galacto-oligosaccharides (GOS) that are fermented by gut bacteria | All subtypes |
| Cow's milk & soft cheese | Lactose is poorly digested in lactose-intolerant individuals, causing gas and loose stools | IBS-D |
| Fatty or fried foods | Stimulate the gastrocolic reflex, accelerating gut transit and potentially causing cramping | IBS-D |
| Coffee & caffeinated tea | Caffeine increases gut motility and can stimulate colonic contractions | IBS-D |
| Alcohol (especially beer & wine) | Irritates the gut lining, increases motility, and beer contains FODMAPs | IBS-D, IBS-M |
| Apples, pears & stone fruits | High in excess fructose and/or sorbitol — both FODMAPs that ferment in the gut | All subtypes |
| Spicy foods | Capsaicin can irritate the gut lining and accelerate transit in sensitive individuals | IBS-D |
| Sugar-free products | Contain polyols (sorbitol, xylitol, mannitol) that draw water into the bowel and ferment | IBS-D, IBS-M |
| Processed ready meals | Often contain hidden FODMAPs (onion powder, garlic powder, inulin) plus emulsifiers and additives | All subtypes |
| Carbonated drinks | Introduce gas directly into the digestive tract, worsening bloating and distension | All subtypes |
Sources: NHS — Irritable bowel syndrome; NICE Clinical Guideline CG61; Monash University FODMAP research
Research from Monash University in Australia — widely endorsed by NHS dietitians — has shown that FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) are among the most significant dietary triggers for IBS symptoms.
FODMAPs are short-chain carbohydrates that are poorly absorbed in the small intestine. When they reach the large intestine, gut bacteria ferment them rapidly, producing hydrogen and methane gas. They also have an osmotic effect, drawing water into the bowel. For people with the visceral hypersensitivity that characterises IBS, this combination of gas and fluid causes disproportionate pain, bloating, and altered bowel habits.
Most people with IBS are sensitive to only one or two FODMAP groups, not all five. Using a FODMAP tracker during the reintroduction phase can help you identify exactly which groups affect you — so you avoid unnecessary food restrictions.
Here is a quick-reference guide to the main categories of IBS triggers. Understanding the mechanism behind each category helps you make more informed food choices.
Onions, garlic, wheat, beans, apples, pears, and honey. These ferment in the gut, producing gas and drawing water into the bowel. The low-FODMAP approach targets these specifically.
Chips, takeaways, fried breakfasts, creamy sauces. Fat stimulates the gastrocolic reflex, which can trigger cramping and urgency — particularly in IBS-D.
Coffee, energy drinks, beer, wine. Both increase gut motility and can irritate the gut lining. Beer is especially problematic as it also contains FODMAPs.
Milk, ice cream, soft cheeses, cream. Lactose intolerance affects around 5% of the UK population, but IBS can increase sensitivity even in those who normally tolerate lactose.
Chilli, hot sauces, curries with capsaicin. The heat compound irritates receptors in the gut, potentially causing pain and accelerated transit in IBS-D.
Ready meals, packet sauces, crisps, processed meats. These often contain hidden FODMAPs (onion powder, garlic powder, inulin) plus emulsifiers and artificial sweeteners.
The low-FODMAP diet is the most evidence-based dietary approach for managing IBS. NICE guidelines recommend it be undertaken with guidance from a dietitian who is trained in the approach. Here is how it works:
All high-FODMAP foods are removed from your diet. This is not a permanent diet — it is a diagnostic tool. If symptoms improve significantly during this phase, it confirms that FODMAPs are contributing to your IBS symptoms.
One FODMAP group is reintroduced at a time, in controlled amounts, over several days. This is the most important phase — it tells you exactly which FODMAP groups trigger your symptoms and at what quantity. A detailed IBS food diary is essential during this phase to track what you eat and how you feel.
Based on your reintroduction results, you create a personalised long-term diet that avoids only the specific FODMAP groups and amounts that trigger your symptoms. The goal is the least restrictive diet that manages your symptoms effectively.
The low-FODMAP diet should not be followed long-term in its elimination phase. Restricting all FODMAPs indefinitely can reduce the diversity of your gut bacteria and lead to nutritional gaps. The reintroduction and personalisation phases are essential for a healthy, balanced approach.
Even when you think you are eating carefully, processed foods can contain hidden ingredients that trigger IBS symptoms. Here are the most common culprits found in UK supermarket products:
The front of a package can say "natural" or "wholesome" while the back reveals onion powder, inulin, or sorbitol. Using a food ingredient scanner can help you spot hidden triggers quickly, especially when you are still learning which ingredients to look out for.
IBS is not purely a food issue. The gut-brain axis plays a significant role, and NICE guidelines acknowledge that psychological factors can both trigger and worsen IBS symptoms. Common non-food triggers include:
This is why a comprehensive food and symptom diary that also tracks stress, sleep, and other factors can be more revealing than logging food alone. It helps you understand the full picture of what drives your symptoms.
Both the NHS and NICE recommend a food and symptom diary as one of the first steps in managing IBS. Here is why tracking is so valuable for IBS specifically:
A detailed food diary also provides your GP or dietitian with concrete data rather than vague descriptions. It helps move the conversation from "everything seems to set me off" to "I have identified three specific triggers and one stacking pattern."
While IBS is a functional condition that is managed rather than cured, the NHS advises seeing your GP if you experience:
Your GP can run tests to rule out other conditions — such as coeliac disease, inflammatory bowel disease (IBD), or food allergies — before confirming an IBS diagnosis. A referral to a dietitian for low-FODMAP guidance may also be available through the NHS.
NutraSafe makes it easy to log meals, scan ingredients for hidden FODMAPs, and track how you feel — helping you spot patterns, identify your personal triggers, and take your food diary to your next GP or dietitian appointment.
Download Free on the App StoreCommon IBS triggers include high-FODMAP foods (onions, garlic, wheat, beans, certain fruits), fatty or fried foods, caffeine, alcohol, spicy foods, and artificial sweeteners. However, triggers vary significantly between individuals and between IBS subtypes (IBS-D, IBS-C, and IBS-M). The NHS recommends keeping a food diary to identify your personal triggers rather than relying on generic lists alone.
The low-FODMAP diet is a three-phase approach developed by Monash University and endorsed by NICE for IBS management. Phase 1 eliminates high-FODMAP foods for 2-6 weeks. Phase 2 systematically reintroduces one FODMAP group at a time over 6-8 weeks to identify your specific triggers. Phase 3 is a personalised long-term diet based on your results. It should ideally be followed with guidance from a registered dietitian.
Yes. IBS-D (diarrhoea-predominant) is often worsened by fatty foods, caffeine, alcohol, spicy foods, and high-fructose items that accelerate gut transit. IBS-C (constipation-predominant) may be aggravated by low-fibre processed foods, excessive dairy, and inadequate fluid intake. IBS-M (mixed) can react to triggers from both subtypes, often unpredictably. This is why personalised tracking is more helpful than a one-size-fits-all approach.
Yes, the gut-brain connection plays a significant role in IBS. Stress, anxiety, and poor sleep can worsen IBS symptoms independently of food triggers. This is acknowledged in NICE guidelines, which recommend addressing psychological wellbeing alongside dietary changes. A food and mood diary can help you distinguish between food-related and stress-related flare-ups, giving you a fuller picture of what drives your symptoms.
See your GP if you have persistent changes in bowel habits, abdominal pain or bloating that does not improve, unexplained weight loss, blood in your stools, or symptoms that are significantly affecting your quality of life. Your GP can rule out other conditions such as coeliac disease, inflammatory bowel disease (IBD), or food allergies before diagnosing IBS, and may refer you to a dietitian for low-FODMAP guidance.
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Last updated: February 2026