DIET THERAPY AND DISEASES OF GASTROINTESTINAL TRACT: DIETARY FIBER
The terms “fiber” and “residue” are often misused. Dietary fiber consists of the indigestible parts of plants. It includes cellulose, hemicelluloses, lignin, gums, pectins, and mucilage occurring in the cell structure of plants. Residue refers to the bulk remaining in the lower part of the gastrointestinal tract. It includes the dietary fibers, cells sloughed off from the intestinal mucosa, and intestinal bacteria and their residues. For example, milk contains no dietary fiber, but the lactose in milk is favorable to the growth of certain types of bacteria in the intestine.
Sources of fiber
The structural parts of plants are important sources of fiber. The fiber content of overripe vegetables such as peas and corn is higher than that of young, tender peas or succulent corn. Bran, whole-grain breads and cereals, legumes, vegetables, and fruits are emphasized in high-fiber diets.
Fiber and motility
A high-fiber diet increases peristalsis, shortens the length of time that food wastes remain in the colon, and increases stool volume. A low-fiber intake reduces peristalsis, increases the pressure within the lumen of the colon, increases transit time through the intestinal tract, and results in small, dry stools.
Modifying fiber content of diets
The fiber content may range from high, to low, to fiber-free. The diet is progressively reduced in fiber content in the following ways:
1. Selecting only young tender vegetables.
2. Omitting those foods that have seeds, tough skins, or much structural fiber; for example, berries, celery, corn, cabbage, stalks of asparagus, mature beans, and peas.
3. Peeling fruits and vegetables, such as apples, pears, potatoes, stalks of broccoli.
4. Cooking foods to soften the fiber.
5. Pressing foods through a sieve (pureeing or straining).
6. Using refined cereals and white breads in place of whole-grain cereals and breads.
7. Omitting fruits and vegetables entirely; using only strained juices. Strained fruits and vegetables and ground meats are extremely unpopular.
They have lost appeal in appearance, texture, and in flavor, and are generally regarded as baby foods. These restrictions are now seldom used for patients with peptic ulcer, colitis, or diverticulitis except in early stages of treatment. On the other hand, strained foods are useful for patients with bleeding esophageal varices, for blenderized tube feedings, and for preparation for gastrointestinal surgery.
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GENERAL HEALTH
