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Everyone needs fiber. Scientific research has shown that eating fiber every day benefits your health and well-being.[1] Symptoms of a diet low in this vital nutrient include constipation, tiredness, loss of concentration and poor appetite.[2] In short, a lack of fiber slows you down.
A healthy diet for American adults should provide a daily intake of fiber ranging from 19 to 38 grams per day, according to the Institute of Medicine of the National Academy of Sciences.[3] However, we actually eat considerably less - only 14-17 grams/day.[4] On average, less than 4 out of 100 people are getting enough fiber in their daily diet.[5]
Not all fibers are the same, however. Physiologically, there are three major mechanisms that are likely responsible for different benefits attributed to dietary fiber[6]:
1. Bulking. Insoluble fibers are well known bulking agents (particularly wheat bran). They hold onto water and help to clean out the digestive tract by increasing stool weight.
2. Viscosity. Other types of fiber (particularly beta-glucan from oats and barley, and psyllium) thicken the contents of the intestinal tract, slowing down the absorption of nutrients. These types of dietary fbers are able to slow down or decrease the absorption of cholesterol, glucose and other nutrients because of this viscosity effect.
3. Fermentation. Some fibers are fermented or used as fuel by the resident bacteria within the intestinal tract. The by-products of this fermentation (short-chain fatty acids, primarily acetate, propionate, and butyrate and gases (CO2, H2 and in some individuals, methane or CH4)) are biologically active and can cause a cascade of effects. The full metabolic consequences of intestinal fermentation are not well understood, but are believed to include support for the immune system, enhanced mineral absorption, increased insulin sensitivity, enhanced satiety as well as increased intestinal health.
Hi-maize resistant starch provides some bulking, but not nearly as much as wheat bran. It provides no viscosity or thickening and thus does not reduce cholesterol levels. It is fully fermented and has been shown to increase stool bulk, reduce pH, increase the production of short-chain fatty acids, and promote regularity. Many researchers are investigating metabolism benefits that are believed linked to fermentation, including satiety via hormones linked to appetite and hunger as well as insulin sensitivity effects. For additional information on these studies, please visit www.ResistantStarch.com, which is a portal of information for health professionals on natural resistant starch.
References
[1] ‘Carbohydrates and Dietary Fibre, Lunn J and Butriss JL British Nutrition Foundation, Nutrition Bulletin, Volume 32, Issue 1, Pages 21-64, 2007
[2] Dietary Fibre: Definition, analysis, physiology and health, J Gray, ILSI Europe, Concise Monograph, 2006, Page 3
[3] Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids, Institute of Medicine of the National Academies of Science. 2005. http://www.nap.edu
[4] NHANES 2005-6. www.ars.usda.gov
[5] Marriott et al. Critical Reivews in Food Science and Nutrition (2010) 50:228-58. This data was also discussed in the Report of the Dietary Guidelines Advisory Committee, Chapter D-5 Carbohydrates, 2010 http://www.cnpp.usda.gov/DGAs2010-DGARCReport.htm
[6] Gallaher DD. Chapter 8 - Dietary Fiber. In "Present Knowledge in Nutrition, Ninth Edition, Volume I", Edited by Barbara A. Bowman and Robert M. Russell. International Life Science Institute Press, 2006, Washington, DC., pages 102-110.
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