During a flare, your gut is more sensitive than usual, so the aim is to give it less to react to. Two things matter most. Fat is one: after a high-fat meal, the rectum became progressively more sensitive in people with IBS, but not in healthy volunteers.[1] FODMAPs are the other. These fermentable oligo-, di-, monosaccharides and polyols are poorly absorbed carbohydrates, and in a blinded trial they brought on IBS symptoms in a dose-dependent way.[2] Food choices won't switch off a flare, but they can stop you adding fuel to it.
Should I eat during an IBS flare-up?
Yes. It's tempting to stop eating when your gut hurts, but UK guidelines advise regular meals, taking time to eat, and not skipping meals or leaving long gaps between them.[3] Monash University, where the low-FODMAP diet was developed, suggests three main meals a day plus one or two snacks if you're hungry,[4] with at least 2–3 hours between meals and snacks so FODMAPs don't pile up in one sitting.[5] Traditional IBS advice also steers clear of very large meals,[6] so smaller portions are the safer choice while you're flaring.
What foods help during an IBS flare-up?
Build meals from plain foods that are naturally low in FODMAPs: rice, oats, corn and potatoes; eggs, meat, poultry, fish and firm tofu; vegetables such as carrots, spinach, green beans and bell peppers; and fruits such as kiwifruit, blueberries and citrus.[7][8] Keep the cooking simple. Meat and fish are low in FODMAPs on their own, but breadcrumbs, marinades, gravies and sauces made with onion or garlic are not.[4] Bananas are fine when firm; ripe ones are high in fructans unless the portion is small.[9]
| Meal | Gentle options | Hold back on |
|---|---|---|
| Breakfast | Oat porridge made with lactose-free milk; eggs on gluten-free toast; a firm banana or an orange | Large servings of wheat toast or cereal; apples, pears and dried fruit |
| Lunch | Rice or potatoes with grilled chicken, fish or firm tofu and cooked carrots, spinach or green beans | Onion- or garlic-based soups and sauces; beans and lentils; creamy or fried dishes |
| Dinner | Plainly cooked meat or fish with rice or potatoes and vegetables, flavored with herbs, chives or the green tops of spring onions | Rich, fatty or deep-fried meals; very spicy food; cauliflower and mushrooms; big portions |
| Snacks | A boiled egg, plain popcorn, a small handful of almonds or walnuts, hard cheese, lactose-free yogurt | Sugar-free gum and mints |
| Drinks | Water, herbal tea | More than 3 cups of tea or coffee a day; alcohol; fizzy drinks |
The table is based on FODMAP food data from Monash and on UK dietary guidance.[7][5][10][3] It isn't a tested "flare diet," and no list suits everyone, so stick with foods you already know you tolerate. Simple changes go a long way: in a Swedish trial, traditional advice about how and when to eat (regular meals, smaller portions, and less fat, insoluble fiber, caffeine and gas-producing foods such as beans, cabbage and onions) helped about as many people as a low-FODMAP diet.[6] For more on individual culprits, see our guide to IBS trigger foods.
What should I eat if my flare is mostly diarrhea or constipation?
- Mostly diarrhea: cut down for now on high-fiber foods such as wholegrain bread, brown rice, nuts and seeds, and drink plenty of water to avoid dehydration.[10] Skip sugar-free sweets, mints, gum and soft drinks that contain sorbitol, mannitol or xylitol.[11] More in what to eat with IBS-D.
- Mostly constipation: drink plenty of water and eat more soluble fiber, from foods such as oats, carrots, peeled potatoes and linseeds.[10] Psyllium (ispaghula), a soluble-fiber supplement, is a recommended first-line treatment for IBS; build it up gradually. Avoid wheat bran, which can make IBS symptoms worse.[12] Kiwifruit is worth a try too: two green kiwifruit a day improved bowel movements and comfort in people with IBS-C in a recent trial.[13] More in what to eat with IBS-C.
What should I drink during an IBS flare-up?
Aim for at least 8 cups of fluid a day, mostly water or other non-caffeinated drinks such as herbal tea. UK guidance also suggests keeping tea and coffee to 3 cups a day and cutting back on alcohol and fizzy drinks.[3] Caffeinated coffee stimulates the colon about as strongly as a meal,[14] so a flare is a good time to switch to decaf or herbal tea.
When should I go back to my normal diet?
As soon as your symptoms allow. Monash's dietitians suggest a short spell on a stricter low-FODMAP diet during a flare, then a gradual return to your personalized diet as you improve.[15] After eating too many FODMAPs, symptoms should settle within one to three days of eating strictly low-FODMAP again.[4] Don't stay restricted for weeks "just in case." Four weeks of FODMAP restriction lowered bifidobacteria, a group of gut bacteria considered beneficial,[16] and Monash advises against following the diet more strictly than you need to.[4] If you have, or have had, an eating disorder, talk to your doctor or a dietitian before cutting foods out.[7]
Once you feel better, look back at the day before the flare began: what and how much you ate, how you slept, how stressed you were and, if relevant, where you were in your cycle. A pattern that repeats is worth testing properly with a structured low-FODMAP diet and reintroduction. IBS Clue can help with the looking back: it logs meals from a photo, flags hidden garlic and onion, and shows which meals came before your symptoms.
When should I see a doctor?
See a doctor if diet changes and pharmacy remedies aren't helping,[10] and promptly if you notice warning signs that IBS doesn't explain:[17][18]
- blood in your stool or bloody diarrhea
- weight loss you can't explain
- a fever
- symptoms that wake you at night
- a lump or swelling in your abdomen
- anemia, a family history of bowel cancer, or symptoms that first start after about age 50
Our page on IBS red flags explains each one.