People with IBS may notice that certain foods trigger flare ups or cause constipation. It is in your best interest to steer clear away from these foods. Some examples of these trigger foods are: 1. Processed foods 2. Gluten 3. Alcohol 4. Fried Foods 5. Chocolate 6. Dairy 7. Insoluble Fiber 8. Caffeine 9. Sugar-free sweeteners 10. Beans & Legumes