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Importance of Fiber in Food

Until recently, fiber (roughage) was largely ignored by the scientific community. After all, the term fiber represents a variety of carbohydrates that are not digested, absorbed or used by the body either for fuel or for building body tissue. More recent epidemiological data suggest that a generous daily intake of fiber may promote health are continuing. Findings have been sufficiently positive that one of the Dietary Guidelines encourages increased intake of dietary fiber.

Definition and Types of Fiber

 The definition of fiber can be confusing. For years the major information available about food fiber was the crude fiber content, that is, the residue remaining after the food sample was treated with the solvent, hot acid and hot alkali. The crude fiber content is usually much smaller than the actual fiber content of the food, averaging one fifth - one third the total value in diets containing a wide variety of foods.
            Dietary fiber is the term used to describe the total fiber content of the food. Dietary fiber represents the content of substances that cannot be broken down by human digestive enzymes or absorbed by the gastrointestinal tract. Nearly all, dietary fiber content is contributed by the insoluble structural matter of plants.
            Actually there are many compounds that belong to the category called dietary fiber. The most important of these are under:

1. Cellulose:

2. Hemi-cellulose

3. Lignin

4. Pectin

5. Gums and Mucilages

6. Algal Polysaccharides – from kelp (seaweeds)

7. Indigestible oligosaccharides – from legumes

            Because individual types of fiber differ in solubility and in other physical and chemical properties, the effects they have on health may differ. Just knowing the total intake of dietary fiber is of limited value.

Sources:

Because dietary fiber is composed largely of structural components of the cell walls of the plants, the major sources of fiber are whole grains, legumes, vegetables, fruits and nuts. Animal products are not a source of dietary fiber. The distribution of specific types of fiber varies, even within food groups grains. Good sources of pectin, for example, include apples, cranberries and cherries, but pears and strawberries are low in pectin.

Oatmeal and legumes have a significant gum content. Generally, whole grain is noted for its cellulose content.

The amount and characteristics of dietary fiber may be affected by food processing. Refining of grains, for example, removes nearly all of the fiber. Preparing juice fruit or vegetable does likewise. Peeling apples, peaches, potatoes, and the like removes a fiber-rich part of the plant.

Points of emphasis 

• Increased fiber intake may promote health by promoting normal elimination of waste products of digestion, by promoting satiety, by helping control serum cholesterol and perhaps by other mechanisms.

• Greatly increased fiber intake may reduce absorption of some nutrients.

• Different types of fiber may influence health in different ways.

• Fruits, vegetables, legumes, whole grain products and nuts provide fiber.

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