Although, health experts often suggest upping your fiber intake to help soothe the symptoms of IBS. Oftentimes, fibrous foods, especially gas-producing vegetables (i.e., onions, broccoli, garlic, cauliflower, and beans) can cause painful attacks and uncomfortable gas. The thinking behind increasing fiber is that it reduces IBS-related constipation, by softening and bulking stool to make it easier to pass.