The Worst Foods For Those With Ulcerative Colitis Watch Out For Fiber. Whole grain cereals and breads are difficult to digest and lead to flare ups if you have UC. ... Nuts And Seeds. These foods are difficult to digest and aggravate the symptoms. ... Dairy. ... Unhealthy Fats. ... Caffeine. ... Alcohol. ... Certain Vegetables. ... Spicy Foods. More items... May 5, 2020