Editing Polysaccharide (section)

== Function ==

=== Structure ===
Nutrition polysaccharides are common sources of energy. Many organisms can easily break down starches into glucose; however, most organisms cannot metabolize cellulose or other polysaccharides like [[cellulose]], [[chitin]], and [[arabinoxylan]]s. Some bacteria and protists can metabolize these carbohydrate types. [[Ruminant]]s and [[termite]]s, for example, use microorganisms to process cellulose.<ref>{{Cite web|title=Turning Waste Into Food: Cellulose Digestion – Dartmouth Undergraduate Journal of Science|url=https://sites.dartmouth.edu/dujs/2011/02/03/turning-waste-into-food-cellulose-digestion/|access-date=2021-09-18|website=sites.dartmouth.edu}}</ref>

Even though these complex polysaccharides are not very digestible, they provide important dietary elements for humans. Called [[dietary fiber]], these carbohydrates enhance digestion. The main action of dietary fiber is to change the nature of the contents of the [[gastrointestinal tract]] and how other nutrients and chemicals are absorbed.<ref name=USDA-IOM>{{cite web| title = Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) (2005), Chapter 7: Dietary, Functional and Total fiber.| publisher = US Department of Agriculture, National Agricultural Library and National Academy of Sciences, Institute of Medicine, Food and Nutrition Board| url = http://www.nal.usda.gov/fnic/DRI//DRI_Energy/339-421.pdf| url-status = dead| archive-url = http://archive.wikiwix.com/cache/20111027050903/http://www.nal.usda.gov/fnic/DRI//DRI_Energy/339-421.pdf| archive-date = 2011-10-27}}</ref><ref name=Eastwood/> Soluble fiber binds to [[bile acid]]s in the small intestine, making them less likely to enter the body; this, in turn, lowers [[cholesterol]] levels in the blood.<ref name=Anderson>{{cite journal | vauthors = Anderson JW, Baird P, Davis RH, Ferreri S, Knudtson M, Koraym A, Waters V, Williams CL | display-authors = 6 | title = Health benefits of dietary fiber | journal = Nutrition Reviews | volume = 67 | issue = 4 | pages = 188–205 | date = April 2009 | pmid = 19335713 | doi = 10.1111/j.1753-4887.2009.00189.x | s2cid = 11762029 | url = http://fibercouncil.com/pdfs/Fiber_Review_Paper.pdf | access-date = 2017-10-25 | url-status = dead | archive-url = https://web.archive.org/web/20170810235027/http://www.fibercouncil.com/pdfs/Fiber_Review_Paper.pdf | archive-date = 2017-08-10 }}</ref> Soluble fiber also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces [[short-chain fatty acid]]s as byproducts with wide-ranging physiological activities (discussion below). Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown.<ref>{{cite journal | vauthors = Weickert MO, Pfeiffer AF | title = Metabolic effects of dietary fiber consumption and prevention of diabetes | journal = The Journal of Nutrition | volume = 138 | issue = 3 | pages = 439–42 | date = March 2008 | pmid = 18287346 | doi = 10.1093/jn/138.3.439 | doi-access = free }}</ref>

Not yet formally proposed as an essential macronutrient (as of 2005), dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake.<ref name=USDA-IOM/><ref name=Eastwood>{{cite journal | vauthors = Eastwood M, Kritchevsky D | title = Dietary fiber: how did we get where we are? | journal = Annual Review of Nutrition | volume = 25 | pages = 1–8 | year = 2005 | pmid = 16011456 | doi = 10.1146/annurev.nutr.25.121304.131658 | author-link2 = David Kritchevsky }}</ref><ref name="EFSA, 2010">{{cite journal|title=Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre|journal=EFSA Journal|date=March 25, 2010|volume=8|issue=3|pages=1462|doi=10.2903/j.efsa.2010.1462|url=https://www.efsa.europa.eu/en/efsajournal/pub/1462|doi-access=free}}</ref><ref>{{cite journal | vauthors = Jones PJ, Varady KA | title = Are functional foods redefining nutritional requirements? | journal = Applied Physiology, Nutrition, and Metabolism | volume = 33 | issue = 1 | pages = 118–23 | date = February 2008 | pmid = 18347661 | doi = 10.1139/H07-134 | url = http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn=1715-5312&volume=33&issue=1&startPage=118 | url-status = dead | format = PDF | archive-url = http://archive.wikiwix.com/cache/20111013080027/http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn%3D1715%2D5312%26volume%3D33%26issue%3D1%26startPage%3D118 | archive-date = 2011-10-13 }}</ref>