User:ScotXW/Dietary fiber
From Wikipedia, the free encyclopedia
The dietary fibers or roughage are the indigestible portion of food. For a long time, dietary fiber has been regarded as irksome to digestion and therefore unnecessary to the human diet. Food with higher amounts of dietary fiber take longer to cook and have a much shorter shelf life. In recent times, dietary fiber has been identified as an important component of the human diet and a daily uptake at least 30g of dietary fiber is recommended, see Dietary Reference Intake.
Two types of dietary fiber are roughly distinguished: water soluble and water insoluble fiber. Both types have different effects on digestion, e.g. not all dietary fiber lead to the same degree to flatulence.
Dietary fibers can act by changing the nature of the contents of the gastrointestinal tract and by changing how other nutrients and chemicals are absorbed.[1] Some types of soluble fiber absorb water to become a gelatinous, viscous substance which is fermented by bacteria in the digestive tract. Some types of insoluble fiber have bulking action and are not fermented.[2] Lignin, a major dietary insoluble fiber source, may alter the rate and metabolism of soluble fibers.[3] Other types of insoluble fiber, notably resistant starch, are fully fermented.[4]
Chemically, dietary fiber consists of non-starch polysaccharides such as arabinoxylans, cellulose, and many other plant components such as resistant starch, resistant dextrins, inulin, lignin, waxes, chitins, pectins, beta-glucans, and oligosaccharides.[3] A novel position has been adopted by the US Department of Agriculture to include functional fibers as isolated fiber sources that may be included in the diet.[3] The term "fiber" is something of a misnomer, since many types of so-called dietary fiber are not actually fibrous.
Food sources of dietary fiber are often divided according to whether they provide (predominantly) soluble or insoluble fiber. Plant foods contain both types of fiber in varying degrees, according to the plant's characteristics.
Advantages of consuming fiber are the production of healthful compounds during the fermentation of soluble fiber, and insoluble fiber's ability (via its passive hygroscopic properties) to increase bulk, soften stool, and shorten transit time through the intestinal tract.
A disadvantage of a diet high in fiber is the potential for significant intestinal gas production and bloating. Constipation can occur if insufficient fluid is consumed with a high-fiber diet.