The term "nondigestible" refers to something that cannot be broken down or metabolized by the body, and therefore passes through the digestive system without being absorbed. This can include fibers such as cellulose found in plant materials like vegetables, fruits, and grains, which are essential for maintaining gut health but do not provide any nutritional value. Nondigestible substances also include certain carbohydrates that the body cannot break down, such as resistant starch or oligosaccharides found in some foods like legumes and whole grains. These nondigestible components can have various health benefits, including promoting a healthy gut microbiome, regulating blood sugar levels, and supporting immune function.