Can high-fiber foods really do everything they say they do? Studies have looked at the relationship between high-fiber diets and many diseases, including colon cancer, heart disease and diabetes. Proven benefits of a high-fiber diet include prevention and treatment of constipation, hemorrhoids and diverticulosis.
In addition, certain types of fiber help lower blood cholesterol levels. Dietary fiber comes from the part of plants that are not digested by enzymes in the intestinal tract. Part of it, however, may be digested by bacteria in the lower intestine. Different types of plants have different amounts and types of fiber, including pectin, amber, mucilage, cellulose, hemicellulose and lignin.
Pectin and amber are water-soluble fibers found within plant cells. They delay the digestion of food but do nothing to increase stool. Beans, oat bran, fruits and vegetables contain soluble fiber. In contrast, the fibers in cell walls do not dissolve in water. These include cellulose, hemicellulose and lignin. Such fibers increase faeces and speed up the passage of food through the digestive tract.
Wheat grains and grains contain less soluble fiber, but vegetables and beans are also good sources. Sometimes there is confusion about the difference between crude fiber and dietary fiber. Both are determined by laboratory analysis, but raw fiber is only one-seventh to one-half of the total diet. Insoluble fiber binds water, makes the stool soft and thick.
Therefore, fiber, especially found in whole grain products, is helpful in treating and preventing constipation, hemorrhoids and diverticulosis. Diverticula are bags of the intestinal wall that can become inflamed and painful. It is now known that high fiber diets provide better results once the inflammation is gone. Some types of fiber, however, appear to have a greater effect than others. Fiber derived from oats is more effective at lowering blood cholesterol levels than fiber found in wheat.
Pectin has a similar effect because, in turn, it can lower the amount of cholesterol in the blood. A high-fiber diet may be helpful for people who wish to lose weight. Fiber itself is low in calories, but it gives a “full” feeling due to its ability to absorb water. For example, an apple pie over half a cup of apple juice contains about the same amount of calories.
High-fiber foods often require more chewing, so one cannot eat a large number of calories in a short period of time. Dietary fiber is found only in plant foods: fruits, vegetables, nuts and grains. Meat, milk and eggs have no fibers. The type of food may or may not affect your fiber. Canned and frozen fruits and vegetables contain as much fiber as raw ones. Some types of processing, however, can reduce fiber content.
Drying and crushing, for example, destroys the water-retaining properties of the fiber. Removal of seeds, peels or hulls also reduces fiber content. Whole tomatoes are more fiber than peeled tomatoes, which contain tomato juice. Similarly, whole wheat bread contains more fiber than white bread.
Fiber supplements are sold in a variety of ways from bran pills to pure cellulose. Many laxatives sold as sedatives are actually fiber supplements. The role of Fiber in food is still being investigated.
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