Nondigestible

Nondigestible refers to substances that cannot be broken down by enzymes of the human digestive system in the small intestine. These components pass into the large intestine largely intact, where they may be fermented by gut microbiota or excreted.

In nutrition, nondigestible carbohydrates are typically classified as dietary fiber. They include cellulose, hemicellulose, lignin, and various resistant starches and some oligosaccharides. Many plant-derived polysaccharides resist human amylases and saccharidases, though some are partially fermented in the colon.

Physiological effects: Nondigestible materials add bulk to stool, slow digestion, and reduce postprandial blood glucose responses. Through fermentation by intestinal bacteria, they can produce short-chain fatty acids that support colon health and may influence mineral absorption and immune function. The energy from fermentation is limited and variable, generally less than that from digestible carbohydrates.

Industrial and dietary contexts: In foods, nondigestible carbohydrates are labeled as dietary fiber and are valued for texture, satiety, and health benefits. They are also used as bulking agents or laxatives (e.g., indigestible fiber components). Safety: For most people, increasing nondigestible intake gradually is well tolerated; high amounts can cause gas, bloating, or discomfort.

Distinction: The term nondigestible contrasts with digestible carbohydrates, such as glucose polymers, which are broken down in the small intestine to provide rapid energy.