Cellulose is a type of polysaccharide plant fiber. Polysaccharide fiber is a carbohydrate composed of linked sugar molecules, however, humans lack the enzyme necessary to break cellulose down into component sugars, allowing your body to absorb it.he form of cellulose used in foods is soluble fiber. It is important to eat other food sources containing insoluble fiber, such as wheat bran, vegetables and whole grain, to gain the maximum contribution of fiber to health.