Both are equally effective, as indicated by HealthTap, but Metamucil may work better for those who prefer a natural fiber, while people for whom tolerance is a real concern may choose Citrucel, according to Ask-Curtis. Metamucil is sometimes not tolerated as well as Citrucel, but Citrucel's active ingredient is semisynthetic.
Citrucel's active ingredient is not fermentable and may not cause gas. The active ingredient in Metamucil is psyllium husk, which is partially fermentable and may cause gas, although studies have shown that Metamucil does not result in more gas than Citrucel. Nevertheless, difficulties with tolerating Metamucil have been reported, according to Ask-Curtis. Other differences between Metamucil and Citrucel include Metamucil's demonstrated ability to lower blood sugar and decrease the risk of heart disease, as noted by the National Fiber Council.