IBS Flare-Up: What to Eat, What to Skip and What to Do First

Quick answer: During an IBS flare-up, many people do better with regular, smaller meals, plenty of fluids and a short break from their known triggers, such as alcohol, caffeine, fizzy drinks and high-FODMAP foods. Add fiber slowly, and see a doctor promptly for blood in your stool, unexplained weight loss or symptoms that are new or different.

When IBS flares, the usual question is what to eat in the next few days. This guide is about that narrower moment. For the full list of common triggers and how to spot them on labels, see our guide to foods to avoid with IBS.

What an IBS Flare-Up Is

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) describes the main symptoms of IBS as abdominal pain, often related to bowel movements, along with changes in bowel habits (diarrhea, constipation or both), bloating and a feeling that you have not finished a bowel movement. IBS is chronic, and symptoms may come and go, which is what people mean by a flare-up. The NIDDK links IBS to several factors, including stress, food intolerances or sensitivities, and hormonal changes, noting that women with IBS often have more symptoms during their periods.

First Steps When a Flare Starts

• Keep meals regular and smaller. A clinical summary of the UK's NICE guidance lists regular meals as the first dietary step.
• Drink enough fluids and go easy on alcohol and caffeine, which the same summary advises limiting.
• Pause the foods you already know bother you. You do not need to guess at new ones during a flare.
• Avoid suddenly changing your fiber. The NIDDK warns that too much fiber at once can cause gas, which can trigger IBS symptoms.
• Write down what you eat and how you feel, so that you and your doctor can see what is going on. See our guide to food diary apps.
• Take your usual medicines as prescribed, and ask your doctor about anything new.

Foods and Drinks People Commonly Ease Off

A published review of diet in IBS reported that patients commonly name caffeine, alcohol, spicy foods and fatty foods as triggers, along with milk products, wheat, cabbage, onions and carbonated drinks. The same review noted that the evidence for most specific triggers is limited and conflicting. Use these as a short list of foods to try easing off, not as a list of foods that are bad for everyone.

• Caffeine and alcohol: often named by patients, and the first things many guidelines suggest limiting.
• Fizzy drinks: carbonation can add gas for some people.
• Spicy and fatty foods: commonly reported, though evidence is mixed.
• High-FODMAP foods: the NIDDK says common high-FODMAP foods include certain fruits, vegetables, dairy, wheat and rye, and sweeteners ending in "-ol".
• Large meals: a smaller portion is often easier than a big one.

Fiber During a Flare

The NIDDK says that fiber may help constipation because it makes stool soft and easier to pass, and that research suggests soluble fiber is more helpful in relieving IBS symptoms. It advises increasing fiber gradually and notes that adults are advised to get 22 to 34 grams a day. If you are in the middle of a flare, hold off on big changes, and ask your doctor or dietitian whether to add soluble fiber once it settles.

The Low FODMAP Diet Is a Short Trial

FODMAPs are fermentable carbohydrates. The NIDDK says that your doctor may have you try the low FODMAP diet for a few weeks, and that if symptoms improve, FODMAP foods are slowly reintroduced to see which ones you tolerate. The American College of Gastroenterology's 2021 guideline suggests a limited trial of a low FODMAP diet to improve global IBS symptoms. Because it removes a lot of foods, it is best done with a dietitian and not as a permanent way of eating. For how a FODMAP app compares with an ingredient checker, see Monash FODMAP App vs. Foodsage.

Read Labels During a Flare

A product can contain a trigger you would not guess. Check the ingredient list of any packaged food for sweeteners ending in "-ol" (sugar alcohols such as sorbitol and xylitol), for dairy, wheat and rye ingredients, and for anything else on your personal list. Our guide to foods to avoid with IBS explains how to read an ingredient list for common triggers, and Foodsage lets you add FODMAP as a custom sensitivity, scan a product and see which of its ingredients match.

When It Might Not Be IBS: Warning Signs

IBS does not cause bleeding or weight loss. A BMJ summary of the NICE guidance on IBS lists red flags that call for further investigation: unintentional and unexplained weight loss, rectal bleeding, anaemia, an abdominal or rectal mass, markers of inflammatory bowel disease, and a family history of bowel or ovarian cancer. If you notice any of these, or a change in your usual pattern that persists, see a doctor promptly. Do not assume that a diet change will fix it.

Get Help Building a Plan

A flare-up plan works best when it is individual. A gastroenterologist or registered dietitian can help you work out your triggers, run a low FODMAP trial safely and make sure you are not cutting out foods you need. This guide is general information and is not medical advice. Foodsage does not diagnose or treat any condition.