According to the Metamucil site, Metamucil powder contains psyllium husk, which is a natural soluble fiber derived from Plantago ovata that helps promote digestive and heart health. Citrucel states the active ingredient in its comparable fiber supplement is methylcellulose, an insoluble fiber designed to prevent gas and bloating.
The Citrucel site explains that fiber is the nondigestible part of plant foods that plays a critical role in digestion. All fiber products are either soluble or insoluble and fermentable or nonfermentable. Soluble fiber dissolves in water, insoluble fiber does not. Fermentable fiber can convert to gases in the digestive tract unlike nonfermentable fiber.
The National Fiber Council lists the many nutritional aspects of fiber. A high-fiber diet promotes good digestive health by helping prevent constipation and irregularity. Fiber also lowers the risk of obesity, diabetes, high blood pressure and stroke. It lowers cholesterol levels by absorbing excess cholesterol and fat from the food a person eats.
According to Citrucel, the American Dietetic Association suggests adults consume between 21 and 38 grams of dietary fiber each day, but most adults only get 10 to 15 grams. High-fiber foods include beans, vegetables, fruits and whole grains. Many health care professionals recommend fiber supplements such as Metamucil and Citrucel for help in meeting the recommended daily intake.