Unfortunately, fiber products can increase bloating, belching, or flatulence, even though they benefit many patients with irritable bowel syndrome or constipation. Fiber increases the amount of gas in the colon by altering the bacteria that live there to the type of bacteria that produce gas, particularly methane gas.
Recent studies show that fiber products containing psyllium may slow the passage of gas through the rectum. If you want to keep taking a fiber supplement, start at low doses of a psyllium fiber product, such as a single teaspoon mixed with water each day, and gradually increase the dose. This will lead to a steady adjustment and sometimes better tolerance of the fiber products. You can also try a fiber product that does not contain psyllium to see if you can tolerate it better.