In IBS with diarrhea (IBS-D), loose or watery stools (Bristol types 6 and 7) are the main problem on days when bowel movements aren't normal.[1] Diet can't cure IBS-D, but some foods and drinks reliably make the gut more sensitive or speed it up, and cutting back on them is the first step guidelines recommend.[2] The rest is about finding your personal triggers without ending up on a needlessly narrow diet.
What causes IBS-D?
There isn't one cause. Researchers have linked IBS to the gut-brain connection, changes in gut bacteria, genes and an oversensitive bowel, and the mix probably differs from person to person.[3] Two things are especially relevant to diarrhea:
- A past gut infection. More than 1 in 10 people develop IBS after infectious gastroenteritis,[4] and IBS that starts this way is usually the diarrhea type.[5]
- Bile acid diarrhea. This is a separate condition that is often mistaken for IBS-D. UK guidelines note that up to a third of people labeled with IBS-D may actually have it,[6] and in a systematic review most of those affected responded to a bile acid-binding medicine.[7]
What can I eat with IBS-D?
Plain staples that are low in FODMAPs make a good base: rice, oats and potatoes; eggs, fish, poultry and meat; firm tofu; lactose-free milk and yogurt or hard cheese; cooked carrots, spinach, green beans and bell peppers; and fruits such as kiwifruit, blueberries, citrus and firm bananas.[8][9][10] Cook with little fat, and watch for marinades and sauces made with onion or garlic.[9] Eat regular meals, take time over them, and don't leave long gaps between them.[11]
Which foods should I avoid with IBS-D?
These are the usual suspects. Not all of them will bother you, so test them rather than cutting everything at once.
| Food or drink | Why it can worsen IBS-D |
|---|---|
| Fatty and fried food | A high-fat meal made the rectum more sensitive in people with IBS, but not in healthy volunteers.[12] |
| Coffee and other caffeine | Caffeinated coffee stimulates the colon about as strongly as a meal.[13] NICE suggests no more than 3 cups of tea or coffee a day.[11] |
| Alcohol, especially binges | Binge drinking (4 or more drinks in a day) was linked to more diarrhea the next day, and alcohol's link with symptoms was strongest in IBS-D.[14] |
| Sugar-free sweets, gum and drinks | Sorbitol, mannitol and xylitol are best avoided if you have diarrhea.[11][3] |
| Chili and very spicy food | A meal containing chili caused abdominal pain and burning in people with IBS-D.[15] |
| High-FODMAP foods | Wheat, onion, garlic, beans, lentils, milk and fruits such as apples and pears; cutting them back eased pain, bloating and urgency in IBS-D (see below).[8][9][16] |
| Lots of high-fiber food during a bout of diarrhea | UK advice is to cut down on wholegrain bread, brown rice, nuts and seeds while diarrhea is a problem.[17] |
For the evidence behind each trigger, see our guide to IBS trigger foods.
Does the low-FODMAP diet help IBS-D?
Often, especially for pain and bloating. In the first US trial in IBS-D, 92 adults followed either a low-FODMAP diet or dietary advice based on modified UK (NICE) guidelines for four weeks. The share reporting adequate relief was not significantly different (52% vs 41%). But more people on the low-FODMAP diet had a meaningful drop in abdominal pain (51% vs 23%), and they had bigger improvements in bloating, stool consistency, frequency and urgency.[16] The American College of Gastroenterology recommends a limited trial of the diet for IBS, and the BSG recommends it as a second-line option supervised by a dietitian.[18][2] It's a short elimination followed by reintroduction, not a permanent diet; see our low-FODMAP diet guide.
Should I eat fiber and drink more with IBS-D?
Fiber is a balancing act. In trials, soluble fiber such as psyllium (ispaghula) improves IBS symptoms while wheat bran doesn't,[19] and the BSG recommends soluble fiber as a first-line treatment for IBS.[2] During a bout of diarrhea, though, UK advice is to eat less fiber overall, especially wholegrains, nuts and seeds.[3][17] If you add psyllium, start small, increase slowly and watch how your stools respond.
Diarrhea costs fluid. Drink at least 8 cups a day, mostly water or other non-caffeinated drinks,[11] and more if diarrhea keeps coming back, so you don't get dehydrated.[17] For bad days, loperamide is NICE's first-choice antidiarrheal medicine for IBS;[11] ask a pharmacist how to use it.[17] Logging your stools on the Bristol stool chart shows whether a change is actually working.
When should I see a doctor about IBS-D?
Diarrhea that doesn't settle deserves tests, not just diet changes. The ACG suggests a blood test for celiac disease and a stool test for fecal calprotectin, to rule out inflammatory bowel disease, in people with IBS and diarrhea.[18] If diarrhea persists, ask about bile acid diarrhea: UK guidelines recommend excluding it, with a SeHCAT scan or a fasting blood test (serum 7α-hydroxy-4-cholesten-3-one, or C4), when IBS-D is suspected.[6] See a doctor promptly if you have blood in your stool, unexplained weight loss, fever, anemia, diarrhea that wakes you at night, or symptoms that started after about age 50.[5] More in IBS red flags.