Fiber Supplements Compared: Psyllium, Inulin, Methylcellulose, and Wheat Dextrin

Psyllium husk is the most studied and most commonly recommended fiber supplement, sold under brand names as well as in raw husk or powder form. It's a soluble fiber that forms a gel, and it has the strongest evidence base of the four for both regularity and modest LDL cholesterol reduction. It's also the most likely of the four to cause gas during the first one to two weeks of use, which is standard fermentation-related adjustment rather than a sign of intolerance.

Methylcellulose is a semi-synthetic fiber that is not fermented by gut bacteria, which is its main practical advantage: it produces meaningfully less gas and bloating than psyllium for people who are sensitive to fermentable fibers, at the cost of having less research behind it for benefits beyond regularity specifically.

Wheat dextrin is a soluble, mostly-fermentable fiber that dissolves completely clear in liquid with no gel texture and no grit, which makes it the easiest of the four to add to drinks without noticeably changing taste or texture. It carries a similar fermentation-related gas profile to psyllium during adjustment.

Inulin, often derived from chicory root, is a prebiotic fiber specifically associated with feeding beneficial gut bacteria strains, and shows up frequently in fiber-fortified packaged foods (including some of the products driving the fibermaxxing product trend at major food brands) because it's easy to add to formulations without changing texture much. It also tends to be the most gas-producing of the four per gram for people unaccustomed to it, since it ferments quickly and completely.

None of these are a substitute for whole-food fiber sources in the research on long-term gut microbiome diversity, but each has a legitimate use case: psyllium for general regularity with the strongest evidence base, methylcellulose for people who get uncomfortable gas from fermentable fibers, wheat dextrin for easy addition to beverages, and inulin as a lower-dose prebiotic addition rather than a primary fiber source.