Undigestible

Undigestible refers to substances that cannot be broken down by the digestive system of an organism. This typically occurs because the organism lacks the necessary enzymes or physical mechanisms to process the material. In humans, common examples of undigestible substances include dietary fiber, such as cellulose found in plant cell walls, and certain types of starches. While not broken down for energy, these components play important roles in digestion, such as adding bulk to stool and promoting the growth of beneficial gut bacteria.

Other undigestible materials can include indigestible polymers like plastic, which persist in the environment and can be harmful if ingested by animals. In some cases, undigestible substances can cause digestive distress, such as bloating or constipation, if consumed in large quantities. The concept of undigestibility is specific to the organism; what is undigestible for one species might be a food source for another. For instance, some microorganisms can break down substances that humans cannot. The presence of undigestible material in the diet is a normal physiological process for many animals.