While considered generally healthy, high-fiber foods, particularly those containing insoluble fiber, should be avoided or limited if you’re experiencing nausea or diarrhea, says Haskell. Unlike soluble fiber, which helps absorb excess liquid to make stools more manageable, insoluble fiber doesn’t dissolve in water. Instead, it adds bulk to the stool and helps move food through the digestive tract more quickly, which can aggravate symptoms like diarrhea.
Insoluble fiber is found in cruciferous vegetables, like kale, broccoli, cauliflower, and Brussels sprouts, as well as fruits like blackberries and raspberries. Whole grains, such as brown rice and whole-grain bread, also contain significant amounts of insoluble fiber.
Janulewicz says that these high-fiber foods can be difficult to digest and may irritate the gut, particularly during a flare-up. “Cooking them makes them gentler, but some patients may still need to avoid them,” she says. Instead, opt for foods with soluble fiber, such as cooked oats and applesauce, which are generally easier on the gut and can help manage diarrhea.