Fiber
Fiber is a crucial component of a healthy diet, primarily made up of plant-based substances that are not digestible by human enzymes. It plays a significant role in regulating digestive health by facilitating the passage of food through the gastrointestinal tract and aiding in nutrient absorption. There are two main types of dietary fiber: insoluble and soluble. Insoluble fiber, found in foods like whole grains and vegetables, adds bulk to the stool and helps maintain regular bowel movements, while soluble fiber, present in fruits and legumes, can slow down digestion and aid in blood sugar regulation.
Increasing fiber intake is associated with several health benefits, including promoting feelings of fullness, managing cholesterol levels, and potentially preventing various diseases such as diabetes and gallstones. However, excessive fiber consumption can lead to gastrointestinal issues, especially for individuals with certain health conditions like gastrointestinal surgeries or diabetes-related complications.
For optimal health, a daily intake of 25 to 35 grams of fiber is recommended, yet many people consume significantly less. To enhance fiber intake, incorporating whole grains, fruits, and vegetables into the diet is encouraged, along with considering fiber supplements if necessary. Overall, fiber is an integral part of a balanced diet, contributing to long-term health and wellness.
Subject Terms
Fiber
Biology
Anatomy or system affected: Gastrointestinal system, intestines
Definition: Plant fiber components include hemicelluloses and pectin and are long, threadlike structures. Animal fiber is composed of protein collagen or segments of loose connective tissue in the skin and organ tissue.
Structure and Functions
Dietary fiber helps regulate the passage of food material through the gastrointestinal tract and influences the absorption of various nutrients. It 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. Cellulose is an insoluble unbranched glucose polymer that can absorb relatively large volumes of water. Hemicellulose is the name for a wide variety of polymers of five-carbon sugars. Pectin is a water-soluble polymer that forms gels and binds water, cations, and bile acids. Gums and mucilages are highly branched polysaccharides that form gels and bind water and other organic material. Increased fiber intake may promote health by promoting the normal elimination of waste products of digestion, by promoting satiety, by helping control serum cholesterol, and by other mechanisms. Greatly increased fiber intake, however, may reduce the absorption of some nutrients.
Disorders and Diseases
The ingestion of too much fiber can result in the formation of an obstructing bolus in a narrowed intestinal or esophageal lumen. The purpose of a low-fiber or fiber-restricted diet is to help prevent this occurrence and to rest the gastrointestinal tract. In acute phases of ulcerative colitis, a fiber-restricted diet lessens the pain and stress of defecation by decreasing the weight and bulk of the stool and delaying intestinal transit time.
A low-fiber diet contains approximately two grams of crude fiber. Foods included are refined bread and cereal products, cooked fruits and vegetables that are low in fiber, and juices. Nuts, legumes, and whole-grain bread and cereal products are restricted. Minimal-fiber diets consist of strained fruit and vegetable juices and white potatoes without skins. Milk is limited to two cups per day, as it indirectly contributes to fecal residue even though it contains no fiber. Continued use of a low-fiber diet in refined carbohydrates, however, is believed to cause diverticular disease of the colon. Reduced bulk causes the colonic lumen to narrow.
A high-fiber diet contains increased amounts of foods containing cellulose, hemicelluloses, lignin, and pectin and reduced amounts of refined carbohydrates. Insoluble fibers increase the volume and weight of the residue to maintain the normal size of the colonic lumen and increase gastrointestinal mobility. Soluble fibers, such as gums and pectins, reduce the rate of intestinal absorption, altering the metabolic effects. High fiber intake necessitates increased fluids.
Certain individuals should not be encouraged to increase the amount of fiber in their diet. Those who have had gastric surgery, vagotomy, pyloroplasty or Roux-en-Y, and some diabetics with gastroparesis diabeticorum have less acid secretion or decreased gastrointestinal motility and may encounter bezoar formation, a compacted mass that does not pass into the intestine. The high-fiber diet has been recommended, however, in the treatment or prevention of dumping syndrome, hyperlipidemia, gallstones, diabetes, and many other diseases and disorders.
Fiber is an essential part of the overall health of an individual’s diet, and consumption of fiber may be considered a preventative health measure. Consuming the recommended twenty-five to thirty-five grams of fiber daily regulates the use of sugars in the body, reduces hunger, and regulates blood sugar levels. Most Americans only eat fifteen grams of fiber a day, so attention should be paid to increasing the fiber intake in one’s diet through whole-grain food options, fruits, and vegetables. Fiber supplements are also available.
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