Question: what is the best insoluble fiber supplement?
Answer: Citrucel (methylcellulose) is mainly insoluble fibers that are nonfermentable, so it's less likely to contribute to bloating and gas. Psyllium husk (Metamucil and Konsyl) is rich in both soluble and insoluble fiber. Generally, fiber supplements with mainly insoluble fiber may be a better option for constipation.