Irritable-bowel syndrome can be irritated by foods that may cause constipation, such as refined foods, dairy products, high-protein diets and various beverages, according to WebMD. IBS diarrhea can be triggered by fried or fatty foods, large meals, high-fiber foods, dairy products and various beverages.
Beverages that can irritate IBS include alcohol, carbonated and caffeinated drinks, according to WebMD. Wheat may worsen IBS symptoms in some individuals.
An individual may prevent IBS constipation by drinking eight glasses of water per day, increasing fiber intake, consuming sorbitol-containing foods and eating ground flaxseed, according to WebMD. An individual may prevent IBS diarrhea by eating smaller portions, drinking six to eight glasses of water each day before or after meals, eating a moderate amount of soluble fiber, avoiding foods with extreme temperatures in the same meal and avoiding foods that cause gas.