Carbohydrate

{{short description|Organic compound that consists only of carbon, hydrogen, and oxygen}} {{distinguish|Hydrocarbon}} {{Use mdy dates|date=September 2015}} [[File:Lactose.svg|thumb|class=skin-invert-image|upright=1.25|Lactose is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 glycosidic linkage.]]

A '''carbohydrate''' ({{IPAc-en|ˌ|k|ɑːr|b|oʊ|ˈ|h|aɪ|d|r|eɪ|t}}) is a sugar (saccharide) or a sugar derivative.<ref>{{cite web |title=Carbohydrate |url=https://goldbook.iupac.org/terms/view/09809 |website=IUPAC Gold Book}}</ref> For the simplest carbohydrates, the carbon-to-hydrogen-to-oxygen atomic ratio is 1:2:1, i.e. they are often represented by the empirical formula {{chem2|(CH2O)_{''n''} }}. Together with amino acids, fats, and nucleic acids, the carbohydrates are one of the major families of biomolecules.<ref>{{cite web |url=https://www.ncbi.nlm.nih.gov/books/NBK579927/#top|title=Essentials of Glycobiology|website = National Library of Medicine}}</ref>

Carbohydrates perform numerous roles in living organisms.<ref>{{Lehninger4th|page=293-324}}</ref> Polysaccharides serve as an energy store (e.g., starch and glycogen) and as structural components (e.g., cellulose in plants and chitin in arthropods and fungi). The 5-carbon monosaccharide ribose is an important component of coenzymes (e.g., ATP, FAD and NAD) and the backbone of the genetic molecule known as RNA. The related deoxyribose is a component of DNA. Saccharides and their derivatives play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development.<ref>{{cite book | vauthors = Maton A, Hopkins J, McLaughlin CW, Johnson S, Warner MQ, LaHart D, Wright JD | title = Human Biology and Health | publisher = Prentice Hall | year = 1993 | location = Englewood Cliffs, New Jersey | pages = [https://archive.org/details/humanbiologyheal00scho/page/52 52–59] | isbn = 978-0-13-981176-0 | url-access = registration | url = https://archive.org/details/humanbiologyheal00scho/page/52 }}</ref>

Carbohydrates are central to nutrition and are found in a wide variety of natural and processed foods. Starch is a polysaccharide and is abundant in cereals (wheat, maize, rice), potatoes, and processed food based on cereal flour, such as bread, pizza or pasta. Sugars appear in the human diet mainly as table sugar (sucrose, extracted from sugarcane or sugar beets), lactose (abundant in milk), glucose and fructose, both of which occur naturally in honey, many fruits, and some vegetables. Table sugar, milk, or honey is often added to drinks and many prepared foods such as jam, biscuits, scones and cakes.

==Terminology== The term "carbohydrate" has many synonyms and the definition can depend on context. Terms associated with carbohydrate include "sugar", "saccharide", "glucan",<ref name="avenas">{{cite book |vauthors=Avenas P |year=2012 |chapter=Etymology of main polysaccharide names |veditors=Navard P |title=The European Polysaccharide Network of Excellence (EPNOE) |publisher=Springer-Verlag |location=Wien |chapter-url=https://www.springer.com/cda/content/document/cda_downloaddocument/9783709104200-c1.pdf?SGWID=0-0-45-1364512-p174060193 |access-date=January 28, 2018 |archive-date=February 9, 2018 |archive-url=https://web.archive.org/web/20180209064118/https://www.springer.com/cda/content/document/cda_downloaddocument/9783709104200-c1.pdf?SGWID=0-0-45-1364512-p174060193 }}</ref> and "glucide".<ref name="Matthews"/> In food science the term "carbohydrate" often means any food that is rich in starch (such as cereals, bread and pasta) or simple carbohydrates, or fairly simple sugars such as sucrose (found in candy, jams, and desserts). Carbohydrates can also refer to dietary fiber, like cellulose.<ref name=lpi/><ref>{{cite book | title = Carbohydrates in human nutrition | series = FAO Food and Nutrition Paper – 66 | chapter = Chapter 1 – The role of carbohydrates in nutrition | chapter-url = http://www.fao.org/docrep/w8079e/w8079e07.htm | publisher = Food and Agriculture Organization of the United Nations | access-date = December 21, 2015 | archive-date = December 22, 2015 | archive-url = https://web.archive.org/web/20151222095451/http://www.fao.org/docrep/w8079e/w8079e07.htm | url-status = live }}</ref>

===Saccharides=== The starting point for the discussion of carbohydrates is the saccharides. Monosaccharides are the simplest carbohydrates in that they cannot be hydrolyzed to smaller carbohydrates. Monosaccharides usually have the formula C''m'' (H2O)''n''. Disaccharides (e.g. sucrose) are common as are polysaccharides/oligosaccharides (e.g., starch, cellulose). Saccharides are polyhydroxy aldehydes, ketones as well as derived polymers having linkages of the acetal type. They may be classified according to their degree of polymerization. Many polyols are also classified as carbohydrates. In many carbohydrates the OH groups are appended to or replaced by ''N''-acetyl (e.g., chitin), sulfate (e.g., glycosaminoglycans), carboxylic acid and deoxy modifications (e.g., fucose and sialic acid).<ref name="Matthews">{{cite book | vauthors = Matthews CE, Van Holde KE, Ahern KG | year = 1999 | title = Biochemistry | edition = 3rd | publisher = Benjamin Cummings | isbn = 978-0-8053-3066-3 }}{{page needed|date=January 2018}}</ref> {| class="wikitable" |+ The major dietary carbohydrates |- ! Class (degree of polymerization) !! Subgroup !! Components |- ! rowspan=3 | Sugars (1–2) || Monosaccharides || Glucose, galactose, fructose, xylose |- | Disaccharides || Sucrose, lactose, maltose, isomaltulose, trehalose |- | Polyols || Sorbitol, mannitol |- ! rowspan=2 | Oligosaccharides (3–9) || Malto-oligosaccharides || Maltodextrins |- | Other oligosaccharides || Raffinose, stachyose, fructo-oligosaccharides |- ! rowspan=2 | Polysaccharides (>9) || Starch || Amylose, amylopectin, modified starches |- | Non-starch polysaccharides || Glycogen, Cellulose, Hemicellulose, Pectins, Hydrocolloids |}

===Complex carbohydrates=== [[image:Heparin General Structure V.1.svg|thumb|right|Heparin, a carbohydrate, is a blood anticoagulant.<ref>{{cite journal | vauthors = Alquwaizani M, Buckley L, Adams C, Fanikos J | title = Anticoagulants: A Review of the Pharmacology, Dosing, and Complications | journal = Current Emergency and Hospital Medicine Reports | volume = 1 | issue = 2 | pages = 83–97 | date = June 2013 | pmid = 23687625 | pmc = 3654192 | doi = 10.1007/s40138-013-0014-6 }}</ref>]] {{Main|Glycoconjugates|Glycosylation}} Sugars may be linked to other types of biological molecules to form glycoconjugates. The enzymatic process of glycosylation creates sugars/saccharides linked to themselves and to other molecules by the glycosidic bond, thereby producing glycans. Glycoproteins, proteoglycans and glycolipids are the most abundant glycoconjugates found in mammalian cells. They are found predominantly on the outer cell membrane and in secreted fluids. Glycoconjugates have been shown to be important in cell-cell interactions due to the presence on the cell surface of various glycan binding receptors in addition to the glycoconjugates themselves.<ref name="Ma_2004">{{cite journal |vauthors=Ma BY, Mikolajczak SA, Yoshida T, Yoshida R, Kelvin DJ, Ochi A | title= CD28 T cell costimulatory receptor function is negatively regulated by N-linked carbohydrates | journal=Biochem. Biophys. Res. Commun. | year=2004 | pages=60–7 | volume=317 | issue=1 | pmid=15047148 | doi=10.1016/j.bbrc.2004.03.012| bibcode= 2004BBRC..317...60M }}</ref><ref name="Takahashi_2004">{{cite journal |vauthors=Takahashi M, Tsuda T, Ikeda Y, Honke K, Taniguchi N | title= Role of N-glycans in growth factor signaling | journal= Glycoconj. J. | year=2004 | pages=207–12 | volume=20 | issue=3 | pmid=15090734 | doi= 10.1023/B:GLYC.0000024252.63695.5c| s2cid= 1110879 }}</ref> In addition to their function in protein folding and cellular attachment, the N-linked glycans of a protein can modulate the protein's function, in some cases acting as an on-off switch.<ref name = "immune_glycan"/>

== History == [[File:Baeyer-Volhard LMU 1877.jpg|thumb|Emil Fischer, who elucidated the structure of glucose, with colleagues and student in their laboratory of LMU Munich in 1877.]] The history of carbohydrates, to some extent, is the history of sugar cane, which was first grown in New Guinea. The mass cultivation occurred in India where techniques were developed for the isolation of crystalline sugar.<ref>{{Cite journal |last=Denham |first=Tim |date=October 2011 |title=Early Agriculture and Plant Domestication in New Guinea and Island Southeast Asia |url=https://www.journals.uchicago.edu/doi/10.1086/658682 |journal=Current Anthropology |volume=52 |issue=54 |pages=S161–S512 |doi=10.1086/658682 |issn=0011-3204 |via=The University of Chicago Press Journals|url-access=subscription }}</ref> Cane sugar and its cultivation reached Europe around the 13th Century and then expanded to the New World, where industrialization occurred.

The chemistry and biochemistry of carbohydrates can be traced to 1811. On that year Constantin Kirchhoff discovered that grape sugar (glucose) forms when starch is boiled with acid. The starch industry started the following year. Henri Braconnot discovered in 1819 that sugar is formed through the action of sulfuric acid on cellulose. William Prout, after chemical analyses of sugar and starch by Joseph Louis Gay-Lussac and Thénard, gave this group of substances the group name "saccharine." The term "carbohydrate" was first proposed by German chemist Carl Schmidt in 1844. In 1856, glycogen, a form of carbohydrate storage in animal livers, was discovered by French physiologist Claude Bernard.<ref>{{Cite journal |last=Young |first=F. G. |date=1957-06-22 |title=Claude Bernard and the Discovery of Glycogen |journal=British Medical Journal |volume=1 |issue=5033 |pages=1431–1437 |doi=10.1136/bmj.1.5033.1431 |issn=0007-1447 |pmc=1973429 |pmid=13436813}}</ref> Emil Fischer received the 1902 Nobel Prize in Chemistry for his work on sugars and purines. For the discovery of glucose metabolism, Otto Meyerhof received the 1922 Nobel Prize in Physiology or Medicine. Hans von Euler-Chelpin, together with Arthur Harden, received the 1929 Nobel Prize in Chemistry "for their research on sugar fermentation and the role of enzymes in this process." In 1947, both Bernardo Houssay for his discovery of the role of the pituitary gland in carbohydrate metabolism and Carl and Gerty Cori for their discovery of the conversion of glycogen received the Nobel Prize in Physiology or Medicine. For the discovery of sugar nucleotides in carbohydrate biosynthesis, Luis Leloir received the 1970 Nobel Prize in Chemistry.

The term ''glycobiology''<ref>{{cite web |title=Essentials of Glycobiology |url=https://www.ncbi.nlm.nih.gov/books/NBK579918/ |website=National Library of Medicine |publisher=Cold Spring Harbor Laboratory Press}}</ref> was coined in 1988 by Raymond Dwek to recognize the coming together of the traditional disciplines of carbohydrate chemistry and biochemistry.<ref name="rademacher">{{cite journal |vauthors=Rademacher TW, Parekh RB, Dwek RA | title=Glycobiology| journal=Annu. Rev. Biochem. | year=1988 | pages=785–838 | issue=1 | volume=57 | pmid=3052290 | doi=10.1146/annurev.bi.57.070188.004033}}</ref> This coming together was as a result of a much greater understanding of the cellular and molecular biology of glycans. "Glycoscience" is a field that explores the structures and functions of glycans.<ref>{{cite web | title=U.S. National Research Council Report, ''Transforming Glycoscience: A Roadmap for the Future'' | url=http://dels.nas.edu/Report/Transforming-Glycoscience-Roadmap/13446 | access-date=2012-10-03 | archive-date=2014-10-20 | archive-url=https://web.archive.org/web/20141020030759/http://dels.nas.edu/Report/Transforming-Glycoscience-Roadmap/13446 }}</ref>

==Nutrition== [[File:GrainProducts.jpg|thumb|upright|Grain products: rich sources of carbohydrates]]

Carbohydrate consumed in food yields 3.87 kilocalories of energy per gram for simple sugars,<ref>{{cite web|url=http://ndb.nal.usda.gov/ndb/foods/show/6202|title=Show Foods|work=usda.gov|access-date=June 4, 2014|archive-date=October 3, 2017|archive-url=https://web.archive.org/web/20171003224558/https://ndb.nal.usda.gov/ndb/foods/show/6202}}</ref> and 3.57 to 4.12 kilocalories per gram for complex carbohydrate in most other foods.<ref>{{cite web|url=https://www.fao.org/docrep/006/y5022e/y5022e04.htm|title=Calculation of the Energy Content of Foods – Energy Conversion Factors|work=fao.org|access-date=August 2, 2013|archive-date=May 24, 2010|archive-url=https://web.archive.org/web/20100524003622/http://www.fao.org/DOCREP/006/Y5022E/y5022e04.htm|url-status=live}}</ref> Relatively high levels of carbohydrate are associated with processed foods or refined foods made from plants, including sweets, cookies and candy, table sugar, honey, soft drinks, breads and crackers, jams and fruit products, pastas and breakfast cereals. Refined carbohydrates from processed foods such as white bread or rice, soft drinks, and desserts are readily digestible, and many are known to have a high glycemic index, which reflects a rapid assimilation of glucose. By contrast, the digestion of whole, unprocessed, fiber-rich foods such as beans, peas, and whole grains produces a slower and steadier release of glucose and energy into the body.<ref>{{cite web |url=https://www.diabetes.org.uk/upload/How%20we%20help/catalogue/carb-reference-list-0511.pdf |title=Carbohydrate reference list |website=www.diabetes.org.uk |access-date=October 30, 2016 |archive-date=March 14, 2016 |archive-url=https://web.archive.org/web/20160314193016/https://www.diabetes.org.uk/upload/how%20we%20help/catalogue/carb-reference-list-0511.pdf }}</ref> Animal-based foods generally have the lowest carbohydrate levels, although milk does contain a high proportion of lactose.

Organisms typically cannot metabolize all types of carbohydrate to yield energy. Glucose is a nearly universal and accessible source of energy. Many organisms also have the ability to metabolize other monosaccharides and disaccharides but glucose is often metabolized first. In ''Escherichia coli'', for example, the lac operon will express enzymes for the digestion of lactose when it is present, but if both lactose and glucose are present, the ''lac'' operon is repressed, resulting in the glucose being used first (see: Diauxie). Polysaccharides are also common sources of energy. Many organisms can easily break down starches into glucose; most organisms, however, cannot metabolize cellulose or other polysaccharides such as chitin and arabinoxylans. These carbohydrate types can be metabolized by some bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose, fermenting it to caloric short-chain fatty acids. Even though humans lack the enzymes to digest fiber, dietary fiber represents an important dietary element for humans. Fibers promote healthy digestion, help regulate postprandial glucose and insulin levels, reduce cholesterol levels, and promote satiety.<ref>{{cite journal | vauthors = Pichon L, Huneau JF, Fromentin G, Tomé D | title = A high-protein, high-fat, carbohydrate-free diet reduces energy intake, hepatic lipogenesis, and adiposity in rats | journal = The Journal of Nutrition | volume = 136 | issue = 5 | pages = 1256–1260 | date = May 2006 | pmid = 16614413 | doi = 10.1093/jn/136.5.1256 | doi-access = free }}</ref>

The Institute of Medicine recommends that American and Canadian adults get between 45 and 65% of dietary energy from whole-grain carbohydrates.<ref>Food and Nutrition Board (2002/2005). ''[https://archive.today/20070210182833/http://newton.nap.edu/books/0309085373/html Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids]''. Washington, D.C.: The National Academies Press. Page [http://newton.nap.edu/books/0309085373/html/769.html 769] {{Webarchive|url=https://web.archive.org/web/20060912060636/http://newton.nap.edu/books/0309085373/html/769.html |date=September 12, 2006 }}. {{ISBN|0-309-08537-3}}.</ref> The Food and Agriculture Organization and World Health Organization jointly recommend that national dietary guidelines set a goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates).<ref>Joint WHO/FAO expert consultation (2003). ''[https://web.archive.org/web/20110423051140/http://www.who.int/hpr/NPH/docs/who_fao_expert_report.pdf]'' (PDF). Geneva: World Health Organization. pp. 55–56. {{ISBN|92-4-120916-X}}.</ref> A 2017 Cochrane Systematic Review concluded that there was insufficient evidence to support the claim that whole grain diets can affect cardiovascular disease.<ref name="pmid28836672">{{cite journal | vauthors = Kelly SA, Hartley L, Loveman E, Colquitt JL, Jones HM, Al-Khudairy L, Clar C, Germanò R, Lunn HR, Frost G, Rees K | display-authors = 6 | title = Whole grain cereals for the primary or secondary prevention of cardiovascular disease | journal = The Cochrane Database of Systematic Reviews | volume = 8 | issue = 8 | article-number = CD005051 | date = August 2017 | pmid = 28836672 | pmc = 6484378 | doi = 10.1002/14651858.CD005051.pub3 | url = https://spiral.imperial.ac.uk:8443/bitstream/10044/1/54579/2/Kelly_et_al-2017-.pdf | access-date = September 27, 2018 | archive-url = https://web.archive.org/web/20180928044051/https://spiral.imperial.ac.uk:8443/bitstream/10044/1/54579/2/Kelly_et_al-2017-.pdf | archive-date = September 28, 2018 }}</ref>

Carbohydrates are one of the main components of insoluble dietary fiber. Although it is not digestible by humans, cellulose and insoluble dietary fiber generally help maintain a healthy digestive system by facilitating bowel movements.<ref name="lpi">{{cite web|url=https://lpi.oregonstate.edu/mic/other-nutrients/fiber|title=Fiber|publisher=Micronutrient Information Center, Linus Pauling Institute, Oregon State University|date=March 2019|access-date=19 January 2025}}</ref> Other polysaccharides contained in dietary fiber include resistant starch and inulin, which feed some bacteria in the microbiota of the large intestine, and are metabolized by these bacteria to yield short-chain fatty acids.<ref name=lpi/><ref name="CRC Handbook of Dietary Fiber in Human Nutrition">{{cite book| vauthors = Cummings JH | title=The Effect of Dietary Fiber on Fecal Weight and Composition| date=2001| publisher=CRC Press| location=Boca Raton, Florida| isbn=978-0-8493-2387-4| page=184| edition=3rd| url=https://www.crcpress.com/CRC-Handbook-of-Dietary-Fiber-in-Human-Nutrition-Third-Edition/Spiller/p/book/9780849323874| access-date=April 24, 2022| archive-date=April 2, 2019| archive-url=https://web.archive.org/web/20190402203003/https://www.crcpress.com/CRC-Handbook-of-Dietary-Fiber-in-Human-Nutrition-Third-Edition/Spiller/p/book/9780849323874| url-status=live}}</ref><ref>{{cite journal | vauthors = Byrne CS, Chambers ES, Morrison DJ, Frost G | title = The role of short chain fatty acids in appetite regulation and energy homeostasis | journal = International Journal of Obesity | volume = 39 | issue = 9 | pages = 1331–1338 | date = September 2015 | pmid = 25971927 | pmc = 4564526 | doi = 10.1038/ijo.2015.84 }}</ref>

===Classification=== The term ''complex carbohydrate'' was first used in the U.S. Senate Select Committee on Nutrition and Human Needs publication ''Dietary Goals for the United States'' (1977) where it was intended to distinguish sugars from other carbohydrates (which were perceived to be nutritionally superior).<ref>Joint WHO/FAO expert consultation (1998), ''Carbohydrates in human nutrition'', [https://www.fao.org/docrep/W8079E/w8079e07.htm chapter 1] {{Webarchive|url=https://web.archive.org/web/20070115102707/http://www.fao.org/docrep/w8079e/w8079e07.htm |date=January 15, 2007 }}. {{ISBN|92-5-104114-8}}.</ref> However, the report put "fruit, vegetables and whole-grains" in the complex carbohydrate column, despite the fact that these may contain sugars as well as polysaccharides. The standard usage, however, is to classify carbohydrates chemically: ''simple'' if they are sugars (monosaccharides and disaccharides) and ''complex'' if they are polysaccharides (or oligosaccharides).<ref name=lpi/><ref name=NutSource>{{cite web|title=Carbohydrates|url=http://www.hsph.harvard.edu/nutritionsource/carbohydrates/|work=The Nutrition Source|publisher=Harvard School of Public Health|access-date=April 3, 2013|date=September 18, 2012|archive-date=May 7, 2013|archive-url=https://web.archive.org/web/20130507074502/http://www.hsph.harvard.edu/nutritionsource/carbohydrates/|url-status=live}}</ref> Carbohydrates are sometimes divided into "available carbohydrates", which are absorbed in the small intestine and "unavailable carbohydrates", which pass to the large intestine, where they are subject to fermentation by the gastrointestinal microbiota.<ref name=lpi/>

====Glycemic index==== The glycemic index (GI) and glycemic load concepts characterize the potential for carbohydrates in food to raise blood glucose compared to a reference food (generally pure glucose).<ref name="lpi-gi">{{cite web |title=Glycemic Index and Glycemic Load |url=https://lpi.oregonstate.edu/mic/food-beverages/glycemic-index-glycemic-load |publisher=Micronutrient Information Center, Linus Pauling Institute, Oregon State University |access-date=19 January 2025 |date=2025}}</ref> Expressed numerically as GI, carbohydrate-containing foods can be grouped as high-GI (score more than 70), moderate-GI (56–69), or low-GI (less than 55) relative to pure glucose (GI=100).<ref name=lpi-gi/> Consumption of carbohydrate-rich, high-GI foods causes an abrupt increase in blood glucose concentration that declines rapidly following the meal, whereas low-GI foods with lower carbohydrate content produces a lower blood glucose concentration that returns gradually after the meal.<ref name=lpi-gi/>

Glycemic load is a measure relating the quality of carbohydrates in a food (low- vs. high-carbohydrate content – the GI) by the amount of carbohydrates in a single serving of that food.<ref name=lpi-gi/>

=== Health effects of dietary carbohydrate restriction ===

{{Main|Low-carbohydrate diet}}  Low-carbohydrate diets may miss the health advantages – such as increased intake of dietary fiber and phytochemicals – afforded by high-quality plant foods such as legumes and pulses, whole grains, fruits, and vegetables.<ref name=mort>{{cite journal | vauthors = Seidelmann SB, Claggett B, Cheng S, Henglin M, Shah A, Steffen LM, Folsom AR, Rimm EB, Willett WC, Solomon SD | display-authors = 6 | title = Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis | journal = The Lancet. Public Health | volume = 3 | issue = 9 | pages = e419–e428 | date = September 2018 | pmid = 30122560 | pmc = 6339822 | doi = 10.1016/s2468-2667(18)30135-x | type = Meta-analysis }}</ref><ref name=fibre>{{cite journal | vauthors = Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L | title = Carbohydrate quality and human health: a series of systematic reviews and meta-analyses | journal = Lancet | volume = 393 | issue = 10170 | pages = 434–445 | date = February 2019 | pmid = 30638909 | doi = 10.1016/S0140-6736(18)31809-9 | url = https://discovery.dundee.ac.uk/ws/files/30375889/Final_Lancet_for_John.pdf | access-date = April 24, 2022 | url-status = live | s2cid = 58632705 | doi-access = free | archive-url = https://web.archive.org/web/20210811080032/https://discovery.dundee.ac.uk/ws/files/30375889/Final_Lancet_for_John.pdf | archive-date = August 11, 2021 | type = Review }}</ref> A "meta-analysis, of moderate quality," included as adverse effects of the diet halitosis, headache and constipation.<ref name=obes>{{cite journal | vauthors = Churuangsuk C, Kherouf M, Combet E, Lean M | title = Low-carbohydrate diets for overweight and obesity: a systematic review of the systematic reviews | journal = Obesity Reviews | volume = 19 | issue = 12 | pages = 1700–1718 | date = December 2018 | pmid = 30194696 | doi = 10.1111/obr.12744 | url = http://eprints.gla.ac.uk/168899/1/168899.pdf | access-date = April 24, 2022 | url-status = live | type = Systematic review | s2cid = 52174104 | archive-url = https://web.archive.org/web/20190923071822/http://eprints.gla.ac.uk/168899/1/168899.pdf | archive-date = September 23, 2019 }}</ref>{{Better source needed|reason=Quoting source: "Only one meta-analysis, of moderate quality, reported adverse effects of LCDs [...]"|date=August 2022}}

Carbohydrate-restricted diets can be as effective as low-fat diets in helping achieve weight loss over the short term when overall calorie intake is reduced.<ref name=endo>{{cite journal | vauthors = Schwartz MW, Seeley RJ, Zeltser LM, Drewnowski A, Ravussin E, Redman LM, Leibel RL | title = Obesity Pathogenesis: An Endocrine Society Scientific Statement | journal = Endocrine Reviews | volume = 38 | issue = 4 | pages = 267–296 | date = August 2017 | pmid = 28898979 | pmc = 5546881 | doi = 10.1210/er.2017-00111 }}</ref> An Endocrine Society scientific statement said that "when calorie intake is held constant [...] body-fat accumulation does not appear to be affected by even very pronounced changes in the amount of fat vs carbohydrate in the diet."<ref name=endo/> In the long term, low-carbohydrate diets do not appear to confer a "metabolic advantage," and effective weight loss or maintenance depends on the level of calorie restriction,<ref name=endo/> not the ratio of macronutrients in a diet.<ref name=tob>{{cite book |chapter=Behavioral approaches to the treatment of obesity |vauthors=Butryn ML, Clark VL, Coletta MC |title=Textbook of Obesity | veditors = Akabas SR, Lederman SA, Moore BJ |publisher=John Wiley & Sons|location=New York|year=2012 |quote=Taken together, these findings indicate that calorie intake, not macronutrient composition, determines long-term weight loss maintenance.|isbn=978-0-470-65588-7|page=259}}</ref> The reasoning of diet advocates that carbohydrates cause undue fat accumulation by increasing blood insulin levels, but a more balanced diet that restricts refined carbohydrates can also reduce serum glucose and insulin levels and may also suppress lipogenesis and promote fat oxidation.<ref>{{cite journal | vauthors = Lopes da Silva MV, de Cassia Goncalves Alfenas R | title = Effect of the glycemic index on lipid oxidation and body composition | journal = Nutrición Hospitalaria | volume = 26 | issue = 1| pages = 48–55 | date = 2011 | doi = 10.3305/nh.2011.26.1.5008 | doi-broken-date = September 5, 2025 | pmid = 21519729 }}</ref> However, as far as energy expenditure itself is concerned, the claim that low-carbohydrate diets have a "metabolic advantage" is not supported by clinical evidence.<ref name=endo/><ref name=hall>{{cite journal | vauthors = Hall KD | title = A review of the carbohydrate-insulin model of obesity | journal = European Journal of Clinical Nutrition | volume = 71 | issue = 3 | pages = 323–326 | date = March 2017 | pmid = 28074888 | doi = 10.1038/ejcn.2016.260 | type = Review | s2cid = 54484172 }}</ref> Further, it is not clear how low-carbohydrate dieting affects cardiovascular health, although two reviews showed that carbohydrate restriction may improve lipid markers of cardiovascular disease risk.<ref name=man>{{cite journal | vauthors = Mansoor N, Vinknes KJ, Veierød MB, Retterstøl K | title = Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials | journal = The British Journal of Nutrition | volume = 115 | issue = 3 | pages = 466–479 | date = February 2016 | pmid = 26768850 | doi = 10.1017/S0007114515004699 | s2cid = 21670516 | doi-access = free }}</ref><ref name=ght>{{cite journal | vauthors = Gjuladin-Hellon T, Davies IG, Penson P, Amiri Baghbadorani R | title = Effects of carbohydrate-restricted diets on low-density lipoprotein cholesterol levels in overweight and obese adults: a systematic review and meta-analysis | journal = Nutrition Reviews | volume = 77 | issue = 3 | pages = 161–180 | date = March 2019 | pmid = 30544168 | doi = 10.1093/nutrit/nuy049 | url = http://researchonline.ljmu.ac.uk/id/eprint/8898/1/nutr-rev%20corrected%20version%2007072018.pdf | access-date = April 24, 2022 | url-status = live | type = Systematic review | s2cid = 56488132 | doi-access = free | archive-url = https://web.archive.org/web/20200506070047/http://researchonline.ljmu.ac.uk/id/eprint/8898/1/nutr-rev%20corrected%20version%2007072018.pdf | archive-date = May 6, 2020 }}</ref>

Carbohydrate-restricted diets are no more effective than a conventional healthy diet in preventing the onset of type 2 diabetes, but for people with type 2 diabetes, they are a viable option for losing weight or helping with glycemic control.<ref name=brouns>{{cite journal | vauthors = Brouns F | title = Overweight and diabetes prevention: is a low-carbohydrate-high-fat diet recommendable? | journal = European Journal of Nutrition | volume = 57 | issue = 4 | pages = 1301–1312 | date = June 2018 | pmid = 29541907 | pmc = 5959976 | doi = 10.1007/s00394-018-1636-y | type = Review }}</ref><ref name=meng>{{cite journal | vauthors = Meng Y, Bai H, Wang S, Li Z, Wang Q, Chen L | title = Efficacy of low carbohydrate diet for type 2 diabetes mellitus management: A systematic review and meta-analysis of randomized controlled trials | journal = Diabetes Research and Clinical Practice | volume = 131 | pages = 124–131 | date = September 2017 | pmid = 28750216 | doi = 10.1016/j.diabres.2017.07.006 }}</ref><ref name=ada/> There is limited evidence to support routine use of low-carbohydrate dieting in managing type 1 diabetes.<ref name=ups>{{cite journal | vauthors = Seckold R, Fisher E, de Bock M, King BR, Smart CE | title = The ups and downs of low-carbohydrate diets in the management of Type 1 diabetes: a review of clinical outcomes | journal = Diabetic Medicine | volume = 36 | issue = 3 | pages = 326–334 | date = March 2019 | pmid = 30362180 | doi = 10.1111/dme.13845 | type = Review | s2cid = 53102654 }}</ref> The American Diabetes Association recommends that people with diabetes should adopt a generally healthy diet, rather than a diet focused on carbohydrate or other macronutrients.<ref name=ada>{{cite journal | vauthors = ((American Diabetes Association Professional Practice Committee)) | title = 5. Lifestyle Management: ''Standards of Medical Care in Diabetes-2019'' | journal = Diabetes Care | volume = 42 | issue = Suppl 1 | pages = S46–S60 | date = January 2019 | pmid = 30559231 | doi = 10.2337/dc19-S005 | url = http://care.diabetesjournals.org/content/42/Supplement_1/S46 | access-date = April 24, 2022 | url-status = live | doi-access = free | archive-url = https://web.archive.org/web/20181218145626/http://care.diabetesjournals.org/content/42/Supplement_1/S46 | archive-date = December 18, 2018 | url-access = subscription }}</ref>

An extreme form of low-carbohydrate diet – the ketogenic diet – is established as a medical diet for treating epilepsy.<ref name=bda-2018/> Through celebrity endorsement during the early 21st century, it became a fad diet as a means of weight loss, but with risks of undesirable side effects, such as low energy levels and increased hunger, insomnia, nausea, and gastrointestinal discomfort.{{scientific citation needed|date=May 2023}}<ref name=bda-2018>{{cite web |publisher=British Dietetic Association |title=Top 5 worst celeb diets to avoid in 2018 |date=7 December 2017 |url=https://www.bda.uk.com/resource/top-5-worst-celeb-diets-to-avoid-in-2018.html |quote=The British Dietetic Association (BDA) today revealed its much-anticipated annual list of celebrity diets to avoid in 2018. The line-up this year includes Raw Vegan, Alkaline, Pioppi and Ketogenic diets as well as Katie Price's Nutritional Supplements. |access-date=1 December 2020 |archive-date=July 31, 2020 |archive-url=https://web.archive.org/web/20200731182316/https://www.bda.uk.com/resource/top-5-worst-celeb-diets-to-avoid-in-2018.html |url-status=live }}</ref> The British Dietetic Association named it one of the "top 5 worst celeb diets to avoid in 2018".<ref name=bda-2018/>

==Sources== thumb|Glucose tablets Most dietary carbohydrates contain glucose, either as their only building block (as in the polysaccharides starch and glycogen), or together with another monosaccharide (as in the hetero-polysaccharides sucrose and lactose).<ref>{{Cite news|url=https://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar/|title=Carbohydrates and Blood Sugar|date=2013-08-05|newspaper=The Nutrition Source|language=en-US|access-date=2017-01-30|via=Harvard T.H. Chan School of Public Health|url-status=live|archive-url=https://web.archive.org/web/20170130010758/https://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar/|archive-date=2017-01-30}}</ref> Unbound glucose is one of the main ingredients of honey. Glucose is extremely abundant and has been isolated from a variety of natural sources across the world, including male cones of the coniferous tree Wollemia nobilis in Rome,<ref>{{cite journal | vauthors = Venditti A, Frezza C, Vincenti F, Brodella A, Sciubba F, Montesano C, Franceschin M, Sergi M, Foddai S, Di Cocco ME, Curini R, Delfini M, Bianco A, Serafini M | display-authors = 6 | title = A syn-ent-labdadiene derivative with a rare spiro-β-lactone function from the male cones of Wollemia nobilis | journal = Phytochemistry | volume = 158 | pages = 91–95 | date = February 2019 | pmid = 30481664 | doi = 10.1016/j.phytochem.2018.11.012 | bibcode = 2019PChem.158...91V | s2cid = 53757166 }}</ref> the roots of Ilex asprella plants in China,<ref>{{cite journal | vauthors = Lei Y, Shi SP, Song YL, Bi D, Tu PF | title = Triterpene saponins from the roots of Ilex asprella | journal = Chemistry & Biodiversity | volume = 11 | issue = 5 | pages = 767–775 | date = May 2014 | pmid = 24827686 | doi = 10.1002/cbdv.201300155 | s2cid = 40353516 }}</ref> and straws from rice in California.<ref>{{cite book | vauthors = Balan V, Bals B, Chundawat SP, Marshall D, Dale BE | chapter = Lignocellulosic Biomass Pretreatment Using AFEX | title = Biofuels | series = Methods in Molecular Biology | volume = 581 | pages = 61–77 | date = 2009 | pmid = 19768616 | doi = 10.1007/978-1-60761-214-8_5 | publisher = Humana Press | isbn = 978-1-60761-213-1 | bibcode = 2009biof.book...61B | place = Totowa, NJ }}</ref> {|class="wikitable sortable" style="text-align:center; margin:auto" |+ Sugar content of selected common plant foods (in grams per 100 g)<ref name="www.nal.usda.gov">{{Cite web|url=https://fdc.nal.usda.gov/index.html|title=FoodData Central|website=fdc.nal.usda.gov}}</ref> |- ! Food item ! Carbohydrate, total,{{ref|2|A}} including dietary fiber ! Total sugars ! Free fructose ! Free glucose ! Sucrose ! Ratio of fructose/ glucose ! Sucrose as proportion of total sugars (%) |- !colspan=8 style="text-align:left"| Fruits |- | style="text-align:left;" | Apple || 13.8|| 10.4|| 5.9|| 2.4|| 2.1|| 2.0|| 19.9 |- | style="text-align:left;" | Apricot|| 11.1|| 9.2|| 0.9|| 2.4|| 5.9|| 0.7|| 63.5 |- | style="text-align:left;" | Banana|| 22.8|| 12.2|| 4.9|| 5.0|| 2.4|| 1.0|| 20.0 |- | style="text-align:left;" | Fig, dried|| 63.9|| 47.9|| 22.9|| 24.8|| 0.9|| 0.93|| 0.15 |- | style="text-align:left;" | Grapes|| 18.1|| 15.5|| 8.1|| 7.2|| 0.2|| 1.1|| 1 |- | style="text-align:left;" | Navel orange|| 12.5|| 8.5|| 2.25|| 2.0|| 4.3|| 1.1|| 50.4 |- | style="text-align:left;" | Peach|| 9.5|| 8.4|| 1.5|| 2.0|| 4.8|| 0.9|| 56.7 |- | style="text-align:left;" | Pear|| 15.5|| 9.8|| 6.2|| 2.8|| 0.8|| 2.1|| 8.0 |- | style="text-align:left;" | Pineapple|| 13.1|| 9.9|| 2.1|| 1.7|| 6.0|| 1.1|| 60.8 |- | style="text-align:left;" | Plum|| 11.4|| 9.9|| 3.1|| 5.1|| 1.6|| 0.66|| 16.2 |- !colspan=8 style="text-align:left"| Vegetables |- | style="text-align:left;" | Beet, red|| 9.6|| 6.8|| 0.1|| 0.1|| 6.5||1.0|| 96.2 |- | style="text-align:left;" | Carrot|| 9.6|| 4.7|| 0.6|| 0.6|| 3.6|| 1.0|| 77 |- | style="text-align:left;" | Red pepper, sweet|| 6.0|| 4.2|| 2.3|| 1.9|| 0.0|| 1.2|| 0.0 |- | style="text-align:left;" | Onion, sweet|| 7.6|| 5.0|| 2.0|| 2.3|| 0.7|| 0.9|| 14.3 |- | style="text-align:left;" | Sweet potato||20.1|| 4.2|| 0.7|| 1.0|| 2.5|| 0.9|| 60.3 |- | style="text-align:left;" | Yam|| 27.9|| 0.5|| {{n/a|Traces}}|| {{n/a|Traces}}|| {{n/a|Traces}}|| {{n/a}}|| {{n/a|Traces}} |- | style="text-align:left;" | Cassava|| 38.1|| 1.7|| {{n/a|Traces}}|| {{n/a|Traces}}|| {{n/a|Traces}}|| {{n/a}}|| {{n/a|Traces}} |- | style="text-align:left;" | Sugar cane|| || 13–18|| 0.2–1.0|| 0.2–1.0|| 11–16|| 1.0|| high |- | style="text-align:left;" | Sugar beet|| || 17–18|| 0.1–0.5|| 0.1–0.5|| 16–17|| 1.0|| high |- !colspan=8 style="text-align:left"| Grains |- | style="text-align:left;" | Corn, sweet|| 19.0|| 6.2|| 1.9|| 3.4|| 0.9|| 0.61|| 15.0 |} {{note|2|A}} The carbohydrate value is calculated in the USDA database and does not always correspond to the sum of the sugars, the starch, and the "dietary fiber".

==Metabolism== {{Main|Carbohydrate metabolism}} Carbohydrate metabolism is the series of biochemical processes responsible for the formation, breakdown and interconversion of carbohydrates in living organisms.

The most important carbohydrate is glucose, a simple sugar (monosaccharide) that is metabolized by nearly all known organisms. Glucose and other carbohydrates are part of a wide variety of metabolic pathways across species: plants synthesize carbohydrates from carbon dioxide and water by photosynthesis storing the absorbed energy internally, often in the form of starch or lipids. Plant components are consumed by animals and fungi, and used as fuel for cellular respiration. Oxidation of one gram of carbohydrate yields approximately 16 kJ (4 kcal) of energy, while the oxidation of one gram of lipids yields about 38 kJ (9 kcal). The human body stores between 300 and 500 g of carbohydrates depending on body weight, with the skeletal muscle contributing to a large portion of the storage.<ref name="Maughan">{{Cite web|url=https://onesearch.cuny.edu/primo-explore/fulldisplay?docid=TN_sciversesciencedirect_elsevierS0263-9319(13)00087-2&context=PC&vid=hc&search_scope=everything&tab=default_tab&lang=en_US|title=Surgery Oxford| vauthors = Maughan R |date=June 2013|website=www.onesearch.cuny.edu}}{{Dead link|date=June 2021 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Energy obtained from metabolism (e.g., oxidation of glucose) is usually stored temporarily within cells in the form of ATP.<ref name="energetics">{{cite web | title = Energetics of Cellular Respiration (Glucose Metabolism) | vauthors = Mehta S | work = Biochemistry Notes, Notes | date = 9 October 2013 | url = http://pharmaxchange.info/press/2013/10/energetics-of-cellular-respiration-glucose-metabolism/ | access-date = October 15, 2015 | archive-date = January 25, 2018 | archive-url = https://web.archive.org/web/20180125234509/http://pharmaxchange.info/press/2013/10/energetics-of-cellular-respiration-glucose-metabolism/ | url-status = live }}</ref> Organisms capable of anaerobic and aerobic respiration metabolize glucose and oxygen (aerobic) to release energy, with carbon dioxide and water as byproducts.

===Catabolism=== Catabolism is the metabolic reaction which cells undergo to break down larger molecules, extracting energy. There are two major metabolic pathways of monosaccharide catabolism: glycolysis and the citric acid cycle.

In glycolysis, oligo- and polysaccharides are cleaved first to smaller monosaccharides by enzymes called glycoside hydrolases. The monosaccharide units can then enter into monosaccharide catabolism. A 2 ATP investment is required in the early steps of glycolysis to phosphorylate Glucose to Glucose 6-Phosphate (G6P) and Fructose 6-Phosphate (F6P) to Fructose 1,6-biphosphate (FBP), thereby pushing the reaction forward irreversibly.<ref name="Maughan"/> In some cases, as with humans, not all carbohydrate types are usable as the digestive and metabolic enzymes necessary are not present.

==Analytical tools== Many techniques are used in the analysis of glycans.<ref name="Cold Spring Harbor Laboratory Press">{{cite book |title=Essentials of Glycobiology |publisher=Cold Spring Harbor Laboratory Press |edition=2nd |year=2009 |isbn=978-0-87969-770-9 |url=http://www.cshlpress.com/default.tpl?action=full&--eqskudatarq=666}}</ref> NMR spectroscopy is common, the major challenge being spectral overlap.<ref>{{cite journal |last1=Fontana |first1=Carolina |last2=Widmalm |first2=Göran |title=Primary Structure of Glycans by NMR Spectroscopy |journal=Chemical Reviews |date=2023 |volume=123 |issue=3 |pages=1040–1102 |doi=10.1021/acs.chemrev.2c00580 |pmid=36622423 |pmc=9912281 }}</ref> <ref>{{Cite journal|last1=Aizpurua-Olaizola|first1=O.|last2=Toraño|first2=J. Sastre|last3=Falcon-Perez|first3=J.M.|last4=Williams|first4=C.|last5=Reichardt|first5=N.|last6=Boons|first6=G.-J.|title=Mass spectrometry for glycan biomarker discovery|journal=TrAC Trends in Analytical Chemistry|volume=100|pages=7–14|doi=10.1016/j.trac.2017.12.015|year=2018|hdl=1874/364403 |hdl-access=free}}</ref>

===High-resolution mass spectrometry (MS) and high-performance liquid chromatography (HPLC)=== MS and HPLC are commonly applied to glycan cleaved either enzymatically or chemically from the target.<ref>{{cite journal |vauthors=Wada Y, Azadi P, Costello CE, etal |title=Comparison of the methods for profiling glycoprotein glycans—HUPO Human Disease Glycomics/Proteome Initiative multi-institutional study |journal=Glycobiology |volume=17 |issue=4 |pages=411–22 |date=April 2007 |pmid=17223647 |doi=10.1093/glycob/cwl086 |doi-access=free }}</ref> In case of glycolipids, they can be analyzed directly without separation of the lipid component.

N-glycans from glycoproteins are analyzed routinely by high-performance-liquid-chromatography (reversed phase, normal phase and ion exchange HPLC) after tagging the reducing end of the sugars with a fluorescent compound (reductive labeling).<ref>{{cite journal |vauthors=Hase S, Ikenaka T, Matsushima Y |title=Structure analyses of oligosaccharides by tagging of the reducing end sugars with a fluorescent compound |journal=Biochem. Biophys. Res. Commun. |volume=85 |issue=1 |pages=257–63 |date=November 1978 |pmid=743278 |doi=10.1016/S0006-291X(78)80037-0 |bibcode=1978BBRC...85..257H }}</ref> A large variety of different labels were introduced in the recent years, where 2-aminobenzamide (AB), anthranilic acid (AA), 2-aminopyridin (PA), 2-aminoacridone (AMAC) and 3-(acetylamino)-6-aminoacridine (AA-Ac) are just a few of them.<ref>{{cite journal |vauthors=Pabst M, Kolarich D, Pöltl G, etal |title=Comparison of fluorescent labels for oligosaccharides and introduction of a new postlabeling purification method |journal=Anal. Biochem. |volume=384 |issue=2 |pages=263–73 |date=January 2009 |pmid=18940176 |doi=10.1016/j.ab.2008.09.041 }}</ref> Different labels have to be used for different ESI modes and MS systems used.<ref>{{Cite journal |last1=Šoić |first1=Dinko |last2=Mlinarić |first2=Zvonimir |last3=Lauc |first3=Gordan |last4=Gornik |first4=Olga |last5=Novokmet |first5=Mislav |last6=Keser |first6=Toma |date=2022 |title=In a pursuit of optimal glycan fluorescent label for negative MS mode for high-throughput N-glycan analysis |journal=Frontiers in Chemistry |volume=10 |article-number=999770 |doi=10.3389/fchem.2022.999770 |pmid=36262345 |pmc=9574008 |bibcode=2022FrCh...10.9770S |issn=2296-2646|doi-access=free }}</ref>

O-glycans are usually analysed without any tags.

Fractionated glycans from high-performance liquid chromatography (HPLC) instruments can be further analyzed by MALDI-TOF-MS(MS) to get further information about structure and purity. Sometimes glycan pools are analyzed directly by mass spectrometry without prefractionation, although a discrimination between isobaric glycan structures is more challenging or even not always possible. Anyway, direct MALDI-TOF-MS analysis can lead to a fast and straightforward illustration of the glycan pool.<ref>{{cite journal |vauthors=Harvey DJ, Bateman RH, Bordoli RS, Tyldesley R |title=Ionisation and fragmentation of complex glycans with a quadrupole time-of-flight mass spectrometer fitted with a matrix-assisted laser desorption/ionisation ion source |journal=Rapid Commun. Mass Spectrom. |volume=14 |issue=22 |pages=2135–42 |year=2000 |pmid=11114021 |doi=10.1002/1097-0231(20001130)14:22<2135::AID-RCM143>3.0.CO;2-# |bibcode=2000RCMS...14.2135H }}</ref>

High performance liquid chromatography online coupled to mass spectrometry is useful. By choosing porous graphitic carbon as a stationary phase for liquid chromatography, even non derivatized glycans can be analyzed. Detection is here done by mass spectrometry, but in instead of MALDI-MS, electrospray ionisation (ESI) is more frequently used.<ref>{{cite journal|last1=Schulz|first1=BL|last2=Packer NH|first2=NH|last3=Karlsson|first3=NG|title=Small-scale analysis of O-linked oligosaccharides from glycoproteins and mucins separated by gel electrophoresis.|journal=Anal. Chem.|volume=74|issue=23|pages=6088–97|pmid=12498206|doi=10.1021/ac025890a|date=Dec 2002}}</ref><ref>{{cite journal |vauthors=Pabst M, Bondili JS, Stadlmann J, Mach L, Altmann F |title=Mass plus retention time equals structure: a strategy for the analysis of N-glycans by carbon LC-ESI-MS and its application to fibrin N-glycans |journal=Anal. Chem. |volume=79 |issue=13 |pages=5051–7 |date=July 2007 |pmid=17539604 |doi=10.1021/ac070363i }}</ref><ref>{{cite journal |vauthors=Ruhaak LR, Deelder AM, Wuhrer M |title=Oligosaccharide analysis by graphitized carbon liquid chromatography-mass spectrometry |journal=Anal Bioanal Chem |volume=394 |issue=1 |pages=163–74 |date=May 2009 |pmid=19247642 |doi=10.1007/s00216-009-2664-5 |doi-access=free }}</ref>

===Multiple reaction monitoring (MRM)=== Although MRM has been used extensively in metabolomics and proteomics, its high sensitivity and linear response over a wide dynamic range make it especially suited for glycan biomarker research and discovery. MRM is performed on a triple quadrupole (QqQ) instrument, which is set to detect a predetermined precursor ion in the first quadrupole, a fragmented in the collision quadrupole, and a predetermined fragment ion in the third quadrupole. It is a non-scanning technique, wherein each transition is detected individually and the detection of multiple transitions occurs concurrently in duty cycles. This technique is being used to characterize the immune glycome.<ref name = "immune_glycan"/><ref>{{Cite journal|last1=Flowers|first1=Sarah A.|last2=Ali|first2=Liaqat|last3=Lane|first3=Catherine S.|last4=Olin|first4=Magnus|last5=Karlsson|first5=Niclas G.|date=2013-04-01|title=Selected reaction monitoring to differentiate and relatively quantitate isomers of sulfated and unsulfated core 1 O-glycans from salivary MUC7 protein in rheumatoid arthritis|journal=Molecular & Cellular Proteomics|volume=12|issue=4|pages=921–931|doi=10.1074/mcp.M113.028878|doi-access=free |issn=1535-9484|pmc=3617339|pmid=23457413}}</ref>

==Chemical synthesis and manipulation of carbohydrates== Carbohydrate synthesis is a sub-field of organic chemistry concerned specifically with the generation of natural and unnatural carbohydrate structures. Carbohydrate chemistry is a large and economically important branch of organic chemistry. This can include the synthesis of monosaccharide residues or structures containing more than one monosaccharide, known as oligosaccharides. Selective formation of glycosidic linkages and selective reactions of hydroxyl groups are very important, and the usage of protecting groups is extensive.

Some of the main organic reactions that involve carbohydrates are: * Amadori rearrangement * Carbohydrate acetalisation * Carbohydrate digestion * Cyanohydrin reaction * Koenigs–Knorr reaction * Lobry de Bruyn–Van Ekenstein transformation * Nef reaction * Wohl degradation * Tipson-Cohen reaction * Ferrier rearrangement * Ferrier II reaction

Related topics * Carbohydrate NMR

==See also== * Gluconeogenesis – A process where glucose can be synthesized by non-carbohydrate sources. * Glycobiology * Glycogen * Glycoinformatics * Glycolipid * Glycome * Glycomics * Glycosyl * Macromolecule * Saccharic acid

== References == {{Reflist}}

== Further reading == * {{cite web |url=https://www.ars.usda.gov/ARSUserFiles/80400525/Data/SR/SR28/sr28_doc.pdf |archive-url=https://web.archive.org/web/20161031150436/https://www.ars.usda.gov/ARSUserFiles/80400525/Data/SR/SR28/sr28_doc.pdf |archive-date=2016-10-31 |url-status=live |title=Compolition of foods raw, processed, prepared |publisher=United States Department of Agriculture|date=September 2015 |access-date=October 30, 2016}}

== External links == {{Commons category|Carbohydrates}} {{wikiquote}} * [https://web.archive.org/web/20130629185521/http://www2.ufp.pt/~pedros/bq/carb_en.htm Carbohydrates, including interactive models and animations] (Requires [https://web.archive.org/web/20060320002451/http://www.mdl.com/products/framework/chime/ MDL Chime]) * [https://web.archive.org/web/20050124032405/http://www.chem.qmw.ac.uk/iupac/2carb/ IUPAC-IUBMB Joint Commission on Biochemical Nomenclature (JCBN): Carbohydrate Nomenclature] * [http://arquivo.pt/wayback/20160516074319/http://www.cem.msu.edu/~reusch/VirtualText/carbhyd.htm Carbohydrates detailed] * [http://biochemweb.fenteany.com/carbohydrates.shtml Carbohydrates and Glycosylation – The Virtual Library of Biochemistry, Molecular Biology and Cell Biology] * [https://www.functionalglycomics.org/ Functional Glycomics Gateway], a collaboration between the Consortium for Functional Glycomics and Nature Publishing Group

Category:Carbohydrates Category:Nutrition