What is fiber?

| Dietary fiber includes carbohydrates ("sugars") of plant origin that are resistant to digestion by our digestive enzymes.

Digestive enzymes act on food, breaking it down to produce very simple compounds that can thus be absorbed through the wall of the intestine. Digestive enzymes act on complex carbohydrates already from the mouth (saliva contains these proteins). When carbohydrates reach the intestine they are partially destroyed by the enzymes in saliva, or they are intact or practically intact (as they were when they were introduced into the mouth).

There, digestive enzymes produced by the pancreas and released into the intestine act again on them. As a consequence of the action of all these digestive enzymes, finally carbohydrates are totally or almost totally destroyed and absorbed. However, there are certain carbohydrates on which our digestive enzymes are not effective and «they escape»To destruction by enzymes and subsequent absorption; these carbohydrates are fiber. But even if fiber escapes the action of human digestive enzymes, this does not mean that it is not digested at all. In fact, a part of the dietary fiber undergoes a process (total or partial) of fermentation in the large intestine by the bacteria that we normally have there, giving rise to compounds such as short-chain fatty acids (acetic acid, propionic acid and butyric acid) that our body and bacteria use.

Composition of dietary fiber

What we include in dietary fiber are substances, some of which are part of the wall of plant cells, giving it the hard structure (not very deformable) typical of these cells; other substances in dietary fiber do not participate as structural elements of plant cells.

Most of the substances that are included in dietary fiber are, from a chemical point of view, carbohydrates (sugars) very complex, such as cellulose, the hemicelluloses, the pectin, the mucilage and the rubbers.

Recently also included in this group are starches and oligosaccharides Indigestible by the digestion proteins in the small intestine, that is, inulin and oligofructose. Other substances that are included in dietary fiber are not carbohydrates: it is the lignin group.