Editing Human nutrition (section)

=== Carbohydrates ===
{{Main|Carbohydrate}}

[[File:GrainProducts.jpg|thumb|upright|[[cereal|Grain]] products: rich sources of complex and simple carbohydrates]]

Carbohydrates may be classified as [[monosaccharide]]s, [[disaccharide]]s or [[polysaccharide]]s depending on the number of monomer (sugar) units they contain. They are a diverse group of substances, with a range of chemical, physical and physiological properties.<ref>{{cite journal | vauthors=Cummings JH, Stephen AM | title=Carbohydrate terminology and classification | journal=European Journal of Clinical Nutrition | volume=61 | pages=S5-18 | date=December 2007 | issue=Suppl 1 | pmid=17992187 | doi=10.1038/sj.ejcn.1602936 | s2cid=3330936 | url=http://www.nature.com.ipacez.nd.edu.au/ejcn/journal/v61/n1s/pdf/1602936a.pdf}}{{dead link|date=May 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> They make up a large part of foods such as [[rice]], [[noodles]], [[bread]], and other [[grain]]-based products,<ref>{{cite web | url=http://www.carb-counter.net/breads/2320 | title=Grams of Carbohydrates in White Bread – Carb Counter | website=www.carb-counter.net | access-date=18 March 2016 | archive-date=31 May 2016 | archive-url=https://web.archive.org/web/20160531092114/http://www.carb-counter.net/breads/2320 | url-status=live}}</ref><ref>{{cite web | url=http://www.amrice.com/6-4.cfm | title=American Rice, Inc. | website=www.amrice.com | access-date=18 March 2016 | archive-date=19 March 2016 | archive-url=https://web.archive.org/web/20160319144117/http://www.amrice.com/6-4.cfm | url-status=dead}}</ref> but they are not an essential nutrient, meaning a human does not need to eat carbohydrates.<ref>{{cite journal | vauthors=Westman EC | title=Is dietary carbohydrate essential for human nutrition? | journal=The American Journal of Clinical Nutrition | volume=75 | issue=5 | pages=951–3; author reply 953–4 | date=May 2002 | pmid=11976176 | doi=10.1093/ajcn/75.5.951a | doi-access=free}}</ref>

Monosaccharides contain one sugar unit, disaccharides two, and polysaccharides three or more. Monosaccharides include [[glucose]], [[fructose]] and [[galactose]].<ref>{{Cite web | url=http://healthyeating.sfgate.com/carbohydrates-contain-monosaccharides-1181.html | title=Carbohydrates That Contain Monosaccharides | website=Healthy eating | date=22 May 2012 | access-date=2015-04-17 | archive-date=2022-10-04 | archive-url=https://web.archive.org/web/20221004231344/https://healthyeating.sfgate.com/carbohydrates-contain-monosaccharides-1181.html | url-status=live}}</ref> Disaccharides include [[sucrose]], [[lactose]], and [[maltose]]; purified [[sucrose]], for instance, is used as table sugar.<ref>{{Cite journal | title=Principles of human nutrition | date=2015 | journal=Medicine | doi=10.1016/j.mpmed.2014.11.009 | volume=43 | issue=2 | pages=61–65 | last1=Lean | first1=Michael E.J. | s2cid=220865321}}</ref> Polysaccharides, which include [[starch]] and [[glycogen]], are often referred to as 'complex' carbohydrates because they are typically long multiple-branched chains of sugar units.

Traditionally, simple carbohydrates were believed to be absorbed quickly, and therefore raise blood-glucose levels more rapidly than complex carbohydrates. This is inaccurate.<ref>{{cite book | last=Otto | first=H | title=Diabetik Bei Diabetus Mellitus | year=1973 | publisher=Verlag Hans Huber | location=Bern}}</ref><ref>{{cite journal | last=Crapo | first=P | author2=Reaven, Olefsky | journal=Diabetes | year=1977 | volume=26 | pages=1178–83 | doi=10.2337/diabetes.26.12.1178 | pmid=590639 | title=Postprandial plasma-glucose and -insulin responses to different complex carbohydrates | issue=12}}</ref><ref>{{cite journal | last=Crapo | first=P | author2=Kolterman, Waldeck | author3=Reaven, Olefsky | journal=Am J Clin Nutr | year=1980 | volume=33 | pages=1723–28 | pmid=6996472 | title=Postprandial hormonal responses to different types of complex carbohydrate in individuals with impaired glucose tolerance | issue=8 | doi=10.1093/ajcn/33.8.1723}}</ref><ref>{{cite journal | last=Jenkins | first=David | author2=Jenkins, Alexandra L. | author3=Wolever, Thomas M.S. | author4=Thompson, Lilian H. | author5=Rao, A. Venkat | doi=10.1111/j.1753-4887.1986.tb07585.x | pmid=3703387 | title=Simple and complex carbohydrates | journal=Nutrition Reviews | date=February 1986 | volume=44 | issue=2 | pages=44–49}}</ref> Some simple carbohydrates (e.g., fructose) follow different metabolic pathways (e.g., [[fructolysis]]) that result in only a partial [[catabolism]] to glucose, while, in essence, many complex carbohydrates may be digested at the same rate as simple carbohydrates.<ref>{{cite web | title=The Nutrition Source: Carbohydrates | url=http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/carbohydrates/index.html | publisher=Harvard School of Public Health | access-date=7 July 2011 | archive-date=7 July 2011 | archive-url=https://web.archive.org/web/20110707013735/http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/carbohydrates/index.html | url-status=live}}</ref> The [[World Health Organization]] recommends that added sugars should represent no more than 10% of total energy intake.<ref>[https://web.archive.org/web/20041204172930/http://whqlibdoc.who.int/trs/WHO_TRS_916.pdf "WHO Technical Report Series. Diet, nutrition and the prevention of chronic diseases."] Report of a Joint WHO/FAO Expert Consultation; Geneva 2003. Retrieved 7 March 2011</ref>

The most common plant carbohydrate nutrient {{ndash}} starch {{ndash}} varies in its absorption. Starches have been classified as rapidly digestible starch, slowly digestible starch and [[resistant starch]].<ref>{{cite journal | last1=Englyst | first1=K.N. | last2=Liu | first2=S. | last3=Englyst | first3=H.N. | title=Nutritional characterization and measurement of dietary carbohydrates | journal=Eur J Clin Nutr | date=2007 | volume=61 | issue=Suppl 1 | pages=S19-39 | doi=10.1038/sj.ejcn.1602937 | pmid=17992185 | s2cid=4218364}}</ref> Starches in plants are resistant to digestion (resistant starch), but cooking the starch in the presence of water can break down the starch granule and releases the glucose chains, making them more easily digestible by human digestive enzymes.<ref>{{cite journal | last1=Wang | first1=Yi | last2=Chen | first2=Long | last3=Yang | first3=Tianyi | last4=Ma | first4=Yun | last5=McClements | first5=David Julian | last6=Ren | first6=Fei | last7=Tian | first7=Yaoqi | last8=Jin | first8=Zhengyu | title=A review of structural transformations and properties changes in starches during thermal processing of foods | journal=Food Hydrocolloids | date=2020 | volume=113 | page=106543 | doi=10.1016/j.foodhyd.2020.106543 | s2cid=230574900 | url=http://www.sciencedirect.com/science/article/pii/S0268005X20329179}}</ref> Historically, food was less processed and starches were contained within the food matrix, making them less digestible.<ref>{{cite journal | last1=Chen | first1=Lying | last2=Liu | first2=Ruining | last3=Qin | first3=Chengyong | last4=Meng | first4=Yan | last5=Zhang | first5=Jie | last6=Wang | first6=Yun | last7=Xu | first7=Guifa | title=Sources and intake of resistant starch in the Chinese diet | journal=Asia Pac J Clin Nutr | date=2010 | volume=19 | issue=2 | pages=274–282 | doi=10.6133/apjcn.2010.19.2.18 | pmid=20460244 | url=http://dx.doi.org/10.6133/apjcn.2010.19.2.18 | access-date=2021-02-26 | archive-date=2023-01-24 | archive-url=https://web.archive.org/web/20230124005339/https://www.airitilibrary.com/Publication/alDetailedMesh?DocID=09647058-201005-201306110032-201306110032-274-282 | url-status=live}}</ref> Modern food processing has shifted carbohydrate consumption from less digestible and resistant starch to much more rapidly digestible starch.<ref name="Lockyer RS Review">{{cite journal | last1=Lockyer | first1=S. | last2=Nugent | first2=A.P. | title=Health effects of resistant starch | journal=Nutrition Bulletin | date=2017 | volume=42 | issue=1 | pages=10–41 | doi=10.1111/nbu.12244 | s2cid=89991088 | doi-access=free}}</ref><ref>{{cite book | last1=Birkett | first1=A.M. | last2=Brown | first2=I.L. | title=Chapter 4: Resistant Starch and Health. In Technology of Functional Cereal Products | date=2008 | publisher=Woodhead Publishing Ltd – CRC Press LLC | location=Boca Raton, FL | isbn=978-1-84569-177-6 | pages=63–85}}</ref> For instance, the resistant starch content of a traditional African diet was 38 grams/day.<ref>{{cite journal | last1=O'Keefe | first1=Stephen J.D. | last2=et | first2=al. | title=Fat, fibre and cancer risk in African Americans and rural Africans | journal=Nat Commun | date=2015 | volume=6 | issue=1 | page=6342 | doi=10.1038/ncomms7342 | pmid=25919227 | pmc=4415091 | bibcode=2015NatCo...6.6342O}}</ref> The resistant starch consumption from countries with high starch intakes has been estimated to be 30-40 grams/day.<ref name="Baghurst Review">{{cite journal | last1=Baghurst | first1=P.A. | last2=Baghurst | first2=K.I. | last3=Record | first3=S.J. | title=Dietary fibre, non-starch polysaccharides and resistant starch – a review | journal=Food Australia | date=1996 | volume=48 | issue=3 | page=S1-S35 | url=http://agris.fao.org/agris-search/search.do?recordID=US201301518409 | access-date=2021-02-26 | archive-date=2022-01-19 | archive-url=https://web.archive.org/web/20220119195548/https://agris.fao.org/agris-search/search.do?recordID=US201301518409 | url-status=live}}</ref> In contrast, the average consumption of resistant starch in the United States was estimated to be 4.9 grams/day (range 2.8-7.9 grams of resistant starch/day).<ref name="Murphy RS Review">{{cite journal | last1=Murphy | first1=M.M. | last2=Douglass | first2=J.S. | last3=Birkett | first3=A. | title=Resistant starch intakes in the United States | journal=J Am Diet Assoc | date=2008 | volume=108 | issue=1 | pages=67–78 | doi=10.1016/j.jada.2007.10.012 | pmid=18155991}}</ref>