Even though humans cannot digest cellulose, it is important in maintaining the health of the intestines by providing fiber. Cellulose is the primary ingredient in the cell walls of plant cells. While most animals cannot digest it, Dummies.com reports it cleanses the colon walls to help prevent cancer.
Cellulose is a long chain of sugars that requires a special enzyme in the digestive tract to break down into energy. Herbivores have this enzyme in their digestive systems, but others in the animal kingdom do not. Since cellulose does not break down, it passes through the stomach and the remainder of the digestive tract unchanged. It does not provide nutrients to the human body, but it causes the waste to move through the digestive tract. Increasing the rate of waste removal from the body prevents reabsorption of sugars by the digestive tract and aids in weight control, according to SFGate.
Manufacturers add cellulose in the form of wood pulp to several foods, such as ice cream and salad dressing. According to the Mayo Clinic, the Food and Drug Administration considers use of such additives as safe, and it imparts a creamy texture to the foods. As an added benefit, the manufacturer is able to reduce fat and sugar without sacrificing the texture or moisture content of the food.