Although high-fiber diets may affect some people with ulcerative colitis during a flare-up, experts generally recommend making sure to get enough fiber during remission. One 2017 review of studies found that it may help prolong periods without inflammation—except for in people who have strictures, or a narrowing of the intestine4. “In those patients, we do advise less fiber, because fibers can clump up and cause an obstruction or blockage,” Dr. Hong says.
2. Foods containing FODMAPs
FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These short-chain carbohydrates are difficult for our bodies to digest, can produce gas, and increase fluid in your colon—ultimately causing diarrhea and gastrointestinal distress in some people. They’re present in an abundance of foods, including onions, legumes, ice cream, apples, honey, and artificial sweeteners.
Experts commonly recommend a low-FODMAP plan to treat irritable bowel syndrome (IBS), a term that describes a collection of symptoms including abdominal pain, bloating, gas, and diarrhea or constipation. People with IBS by definition do not have inflammation in the digestive tract like people with IBD do. However, ulcerative colitis and IBS share some common symptoms5, so your doctor may recommend trying a low-FODMAP diet if you have ulcerative colitis, Dr. Hong says.
Researchers are studying whether low-FODMAP diets can relieve ulcerative colitis flare-ups, but so far studies have been small. A 2016 retrospective study in the journal Inflammatory Bowel Diseases found that a low-FODMAP diet reduced symptoms in 38 ulcerative colitis patients6. More research studying larger numbers of people is necessary to determine whether FODMAPs are a critical factor in ulcerative colitis symptoms. However, anecdotally, some people with ulcerative colitis report that curbing their FODMAP intake seems to help their gut symptoms7.
Initially, the low-FODMAP diet is very restrictive: The idea is to cut out all FODMAPs before slowly reintroducing some to determine which you can tolerate. So, it’s important to work with your health team when making any dietary change to avoid nutritional deficiencies.
3. Cheese, milk, and dairy products
Dairy is tricky, Dr. Hong says, because lactose intolerance—or even a full-blown dairy allergy—can sometimes be mistaken for an ulcerative colitis flare-up. “One of the things we recommend is if you’re feeling unwell with things you’re eating, try cutting out the dairy. If that does help, then maybe get tested for lactose intolerance, which is an easy test to do and is warranted.”
Lactose intolerance and a dairy allergy are very different, even though some of the symptoms are similar, like abdominal cramping and diarrhea. With lactose intolerance, your body doesn’t produce enough lactase, which is an enzyme that allows you to digest lactose, the main sugar found in dairy. Lactose intolerance isn’t an emergency situation, even if it feels like a bathroom emergency. If you have a dairy allergy, you are actually allergic to specific proteins found in dairy products, and your immune system springs into action when you consume them. This can lead to a severe allergic reaction, which can turn life-threatening. No matter which you might be dealing with, you’ll want to rule out a sensitivity to dairy as a cause for your GI discomfort.
4. Foods containing gluten
Ulcerative colitis is not the same as celiac disease, in which gluten triggers the immune system to attack the small intestine. However, 2020 research indicates that people with ulcerative colitis are more likely to also have celiac disease3. Alternatively, you might have gluten sensitivity, meaning you don’t have an immune response to gluten but find it causes symptoms including bloating, abdominal pain, diarrhea, and fatigue, all of which can also be symptoms of ulcerative colitis.