Another important function of fiber is how it affects the absorption of nutrients from your diet. For example, fiber in your meal can slow sugar (glucose) absorption, and lower the glycemic index of that meal. Remember that the glycemic index is a measure of the blood sugar response to certain foods or meals.
Fiber-rich foods generally have a lower glycemic index and when consumed result in less insulin production. This makes fiber especially important for anyone with carbohydrate intolerance. Pectins, mucilages, and especially gums, seem to do this very well. Absorption of minerals is also influenced by fiber, but in a negative way.
Phytic acid, a natural substance present in the fibers of grains and in much smaller amounts in fruits, can inhibit the absorption of calcium, iron, zinc and copper, and possibly other nutrients. For those who may have problems getting enough of these minerals, limiting grains can be helpful.
Absorption of Nutrients
In addition to their relationship to mineral absorption, some fibers may have an adverse effect on digestive enzymes. Wheat bran, for example, can inhibit the production of pancreatic enzymes responsible for digesting carbohydrates, proteins and fats.
The fiber in legumes may inhibit the enzyme amylase, which is important for carbohydrate digestion. Other studies show that the fiber in many cereals contains pancreatic inhibitors that can diminish protein digestion.
In addition, the fiber in unprocessed soybeans can induce an allergy-type reaction in some people, accounting for the intestinal discomfort some may have with soy.