Editing Inulin

{{Short description|Natural plant polysaccharides}}
{{distinguish|insulin}}
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| ImageFile = Inulin strukturformel.svg
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|Section1={{Chembox Identifiers
| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
| DrugBank = DB00638
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| UNII = JOS53KRJ01
| KEGG = D00171
| PubChem = 24763
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| CASNo = 9005-80-5
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|Section2={{Chembox Properties
| Formula = C<sub>6''n''</sub>H<sub>10''n''+2</sub>O<sub>5''n''+1</sub>
| MolarMass= Polymer; depends on ''n''
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|Section6={{Chembox Pharmacology
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'''Inulins''' are a group of naturally occurring [[polysaccharide]]s produced by many types of [[plant]]s,<ref name="Roberfroid 2003 13–26" /> industrially most often extracted from [[chicory]].<ref>{{cite journal | author=Roberfroid M. B. | title=Inulin-type fructans: functional food ingredients | journal=[[Journal of Nutrition]] | volume=137 |issue=11 suppl | year=2007 | pages=2493S–2502S | url=http://jn.nutrition.org/content/137/11/2493S.long | pmid=17951492| doi=10.1093/jn/137.11.2493S | doi-access=free }}</ref> The inulins belong to a class of [[dietary fiber]]s known as [[fructan]]s. Inulin is used by some plants as a means of storing energy and is typically found in [[root]]s or [[rhizome]]s. Most plants that synthesize and store inulin do not store other forms of [[carbohydrate]] such as [[starch]]. In 2018, the United States [[Food and Drug Administration]] approved inulin as a dietary fiber ingredient used to improve the [[nutrition]]al value of manufactured food products.<ref name="fda">{{cite web |title=The Declaration of Certain Isolated or Synthetic Non-Digestible Carbohydrates as Dietary Fiber on Nutrition and Supplement Facts Labels: Guidance for Industry |url=https://www.fda.gov/downloads/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/UCM610144.pdf |archive-url=https://web.archive.org/web/20180725221651/https://www.fda.gov/downloads/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/UCM610144.pdf |url-status=dead |archive-date=July 25, 2018 |publisher=US Food and Drug Administration |access-date=15 June 2018 |date=14 June 2018}}</ref> Using inulin to measure [[kidney function]] is the [[Gold standard (test)|"gold standard"]] for comparison with other means of estimating [[Renal function#Glomerular_filtration_rate|glomerular filtration rate]].<ref>{{cite journal |last1=Hsu |first1=C. Y. |last2=Bansal |first2=N. |title=Measured GFR as 'gold standard'—all that glitters is not gold? |journal=Clinical Journal of the American Society of Nephrology |date=August 2011 |volume=6 |issue=8 |pages=1813–1814 |pmid=21784836 |doi=10.2215/cjn.06040611 |doi-access=free}}</ref>

== Origin and history ==
Inulin is a natural storage carbohydrate present in more than 36,000 species of plants, including [[agave]], [[wheat]], [[onion]], [[banana]]s, [[garlic]], [[asparagus]], [[Jerusalem artichoke]], and [[chicory]]. For these plants, inulin is used as an energy reserve and for regulating cold resistance.<ref name=I1>{{cite journal |last=Niness |first=K. R. |title=Inulin and oligofructose: what are they? |journal=The Journal of Nutrition |date=July 1999 |volume=129 |issue=7 Suppl |pages=1402S–6S |pmid=10395607 |doi=10.1093/jn/129.7.1402S |doi-access=free}}</ref><ref name=I2>{{cite journal |last=Kalyani Nair |first=K. |author2=Kharb, Suman |author3=Thompkinson, D. K. |title=Inulin Dietary Fiber with Functional and Health Attributes—A Review |journal=Food Reviews International |date=18 March 2010 |volume=26 |issue=2 |pages=189–203 |doi=10.1080/87559121003590664|s2cid=84555786 }}</ref> Because it is soluble in water, it is osmotically active. Certain plants can change the [[osmotic potential]] of their cells by changing the degree of [[polymerization]] of inulin molecules by [[hydrolysis]]. By changing osmotic potential without changing the total amount of carbohydrate, plants can withstand cold and drought during winter periods.<ref name=I3>{{cite book |last=Boeckner |first=L. S. |author2=Schnepf, M. I. |author3=Tungland, B. C. |title=Inulin: a review of nutritional and health implications |year=2001 |volume=43 |pages=[https://archive.org/details/advancesinfoodnu0000unse/page/1 1–63] |pmid=11285681 |doi=10.1016/s1043-4526(01)43002-6 |series=Advances in Food and Nutrition Research |isbn=978-0-12-016443-1 |url-access=registration |url=https://archive.org/details/advancesinfoodnu0000unse/page/1}}</ref>

Inulin was discovered in 1804 by German scientist [[Valentin Rose (pharmacologist)|Valentin Rose]]. He found "a peculiar substance" from ''[[Inula helenium]]'' roots by boiling-water extraction.<ref name=I3 /><ref name=I11>{{cite journal |last=Irvine |first=James Colquhoun |author2=Soutar, Charles William |title=CLXV. The constitution of polysaccharides. Part II. The conversion of cellulose into glucose |journal=Journal of the Chemical Society, Transactions |year=1920 |volume=117 |pages=1489–1500 |doi=10.1039/CT9201701489 |url=https://zenodo.org/record/1593106}}</ref> In the 1920s, [[James Irvine (chemist)|J. Irvine]] used chemical methods such as [[methylation]] to study the molecular structure of inulin, and he designed the isolation method for this new [[anhydrous|anhydro]]fructose.<ref name=I11 /><ref name=I12>{{cite journal |last=Irvine |first=James Colquhoun |author2=Stevenson, John Whiteford |title=The molecular structure of inulin. Isolation of a new anhydrofructose |journal=Journal of the American Chemical Society |date=July 1929 |volume=51 |issue=7 |pages=2197–2203 |doi=10.1021/ja01382a035}}</ref> During studies of [[renal tubule]]s in the 1930s, researchers searched for a substance that could serve as a [[biomarker]] that is not reabsorbed or secreted after introduction into tubules.<ref name=I13>{{cite journal |last=Richards |first=A. N. |author2=Westfall, B. B. |author3=Bott, P. A. |title=Renal Excretion of Inulin, Creatinine and Xylose in Normal Dogs |journal=Experimental Biology and Medicine |date=1 October 1934 |volume=32 |issue=1 |pages=73–75 |doi=10.3181/00379727-32-7564P|s2cid=87153900 }}</ref><ref name=I14>{{cite journal |last=Shannon |first=J. A. |author2=Smith, H. W. |title=The excretion of inulin, xylose and urea by normal and phlorinzinized man |journal=The Journal of Clinical Investigation |date=July 1935 |volume=14 |issue=4 |pages=393–401 |pmid=16694313 |doi=10.1172/JCI100690 |pmc=424694}}</ref> [[Alfred Newton Richards|A. N. Richards]] introduced inulin because of its high [[molecular weight]] and its resistance to [[enzyme]]s.<ref name=I13 /> Inulin is used to determine [[glomerular filtration rate]] of the [[kidney]]s.<ref name=I15>{{cite journal |last=Coulthard |first=M. G. |author2=Ruddock, V. |title=Validation of inulin as a marker for glomerular filtration in preterm babies |journal=Kidney International |date=February 1983 |volume=23 |issue=2 |pages=407–409 |pmid=6842964 |doi=10.1038/ki.1983.34|doi-access=free }}</ref>

== Chemical structure and properties ==
Inulin is a heterogeneous collection of [[fructose]] [[polymer]]s. It consists of chain-terminating [[glucosyl]] [[moiety (chemistry)|moieties]] and a repetitive [[fructosyl]] moiety,<ref>Barclay, Thomas, et al. Inulin – a versatile polysaccharide with multiple pharmaceutical and food chemical uses. Diss. International Pharmaceutical Excipients Council, 2010.</ref> which are linked by β(2,1) bonds. The degree of polymerization (DP) of standard inulin ranges from 2 to 60. After removing the fractions with DP lower than 10 during manufacturing process, the remaining product is high-performance inulin.<ref name=I1 /><ref name=I2 /> Some articles considered the fractions with DP lower than 10 as short-chained [[fructo-oligosaccharide]]s, and only called the longer-chained molecules inulin.<ref name=I3 />

Because of the β(2,1) linkages, inulin is not digested by enzymes in the [[Human digestive system|human alimentary system]], contributing to its functional properties: reduced calorie value, dietary fiber, and [[prebiotic (nutrition)|prebiotic]] effects.<ref>Cassella, Carla, ''[https://www.sciencealert.com/a-cheap-daily-supplement-seems-to-boost-brain-function-in-older-people A Cheap Daily Supplement Seems to Boost Brain Function in Older People]'', Science Alert, November 28, 2024 </ref> Without color and odor, it has little impact on sensory characteristics of food products. [[Oligofructose]] has 35% of the sweetness of [[sucrose]], and its sweetening profile is similar to sugar. Standard inulin is slightly sweet, while high-performance inulin is not. Its solubility is higher than the classical fibers. When thoroughly mixed with liquid, inulin forms a gel and a white creamy structure, which is similar to fat. Its three-dimensional gel network, consisting of insoluble submicron crystalline inulin particles, immobilizes a large amount of water, assuring its physical stability.<ref name=I4>{{cite journal |last=Franck |first=A. |title=Technological functionality of inulin and oligofructose |journal=British Journal of Nutrition |date=9 March 2007 |volume=87 |issue=S2 |pages=S287–S291 |doi=10.1079/BJN/2002550 |pmid=12088531 |doi-access=free}}</ref> It can also improve the stability of foams and emulsions.<ref name=I2 />

==Uses==

=== Harvesting and extraction ===
[[Chicory]] root is the main source of [[extract]]ion for commercial production of inulin. The extraction process for inulin is similar to obtaining [[sugar]] from [[sugar beet]]s.<ref name=I1 /> After harvest, the chicory roots are sliced and washed, then soaked in a [[solvent]] (hot water or ethanol);<ref>{{cite web |title=What is Inulin? The Ultimate FAQ Guide to Inulin |url=https://blog.supplementplace.co.uk/nutrition/what-is-inulin/ |website=Supplement Place |access-date=5 November 2022 |date=May 15, 2019}}</ref> the inulin is then isolated, purified, and spray dried. Inulin may also be [[chemical synthesis|synthesized]] from [[sucrose]].<ref name=I1 />

===Processed foods===
Inulin received no-objection status as [[generally recognized as safe]] (GRAS) from the U.S. [[Food and Drug Administration]] (FDA),<ref>{{cite web |title=Agency Response Letter GRAS Notice No. GRN 000118 |url=https://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/NoticeInventory/ucm153932.htm |archive-url=https://web.archive.org/web/20150822003350/http://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/NoticeInventory/ucm153932.htm |url-status=dead |archive-date=August 22, 2015 |publisher=US Food and Drug Administration |author=Rulis, Alan M. |date=5 May 2003}}</ref> including long-chain inulin as GRAS.<ref>{{cite web |title=Agency Response Letter GRAS Notice No. GRN 000576 |url=https://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/NoticeInventory/ucm489503.htm |archive-url=https://web.archive.org/web/20160505004605/http://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/NoticeInventory/ucm489503.htm |url-status=dead |archive-date=May 5, 2016 |publisher=US Food and Drug Administration |date=9 December 2015 |author=Keefe, Dennis M.}}</ref> In the early 21st century, the use of inulin in processed foods was due in part to its adaptable characteristics for manufacturing.<ref name="slavin">{{Cite journal |last=Slavin |first=Joanne |date=2013-04-22 |title=Fiber and Prebiotics: Mechanisms and Health Benefits |journal=Nutrients |volume=5 |issue=4 |pages=1417–1435 |doi=10.3390/nu5041417 |issn=2072-6643 |pmc=3705355 |pmid=23609775|doi-access=free }}</ref> It is approved by the FDA as an ingredient to enhance the dietary fiber value of manufactured foods.<ref name=fda/> Its flavor ranges from bland to subtly sweet (about 10% of the sweetness of sugar/sucrose). It can be used to replace sugar, fat, and flour. This is advantageous because inulin contains 25–35% of the [[food energy]] of carbohydrates (starch, sugar).<ref>{{cite journal | pmid = 10395615 | volume=129 | issue=7 Suppl | title=Caloric value of inulin and oligofructose | journal=J. Nutr. | pages=1436S–7S | last1 = Roberfroid | first1 = M. B. | year=1999| doi=10.1093/jn/129.7.1436S | doi-access=free }}</ref><ref>[http://jn.nutrition.org/content/129/7/1436.full.pdf "Caloric Value of Inulin and Oligofructose"]{{Dead link|date=January 2020 |bot=InternetArchiveBot |fix-attempted=yes }}.</ref> In addition to being a versatile ingredient, inulin provides nutritional advantages by increasing [[calcium]] absorption<ref>{{cite journal |author=Abrams S. |author2=Griffin I. |author3=Hawthorne K. |author4=Liang L. |author5=Gunn S. |author6=Darlington G. |author7=Ellis K. | title = A combination of prebiotic short- and long-chain inulin-type fructans enhances calcium absorption and bone mineralization in young adolescents | journal = Am. J. Clin. Nutr. | volume = 82 | issue = 2 | pages = 471–476 | year = 2005 | pmid = 16087995 | doi=10.1093/ajcn.82.2.471| doi-access = free }}</ref> and possibly [[magnesium]] absorption,<ref>{{cite journal |author=Coudray C. |author2=Demigné C. |author3=Rayssiguier Y. | title = Effects of dietary fibers on magnesium absorption in animals and humans | journal = J. Nutr. | volume = 133 | issue = 1 | pages = 1–4 | year = 2003 | pmid = 12514257| doi = 10.1093/jn/133.1.1 | doi-access = free }}</ref> while promoting the growth of intestinal [[bacteria]].<ref name=slavin/> Chicory inulin is reported to increase absorption of calcium in young women with lower calcium absorption<ref>{{cite journal |last=Griffin |first=I. J. |author2=P. M. Hicks |author3=R. P. Heaney |author4=S. A. Abrams |title=Enriched chicory inulin increases calcium absorption mainly in girls with lower calcium absorption |journal=Nutr. Res. |year=2003 |volume=23 |issue=7 |pages=901–909 |doi=10.1016/s0271-5317(03)00085-x}}</ref> and in young men.<ref name="Roberfroid 2003 13–26">{{cite journal |last=Roberfroid |first=M. B. |title=Introducing inulin-type fructans |journal=Br. J. Nutr. |year=2003 |volume=93 |pages=13–26 |doi=10.1079/bjn20041350 |pmid=15877886 |doi-access=free}}</ref> In terms of nutrition, it is considered a form of [[Dietary fiber|soluble fiber]] and is sometimes categorized as a prebiotic. It is also considered a [[FODMAP]], a class of carbohydrates which are rapidly fermented in the [[large intestine|colon]] producing gas.<ref name=slavin/> Although FODMAPs may cause certain digestive discomfort in some people, they produce potentially favorable alterations in the [[intestinal flora]] that contribute to maintaining health of the colon.<ref name="MakhariaCatassi2015">{{cite journal |author=Makharia A. |author2=Catassi C. |author3=Makharia G. K. |title=The Overlap between Irritable Bowel Syndrome and Non-Celiac Gluten Sensitivity: A Clinical Dilemma |journal=Nutrients |year= 2015 |volume= 7 |issue=12 |pages=10417–26 |pmid=26690475 |doi=10.3390/nu7125541 |pmc=4690093 |type=Review |doi-access=free }} </ref><ref name="GreerOKeefe2015">{{cite journal |author=Greer J. B. |author2=O'Keefe S. J. |title=Microbial induction of immunity, inflammation, and cancer |journal=Front Physiol |year=2011 |volume=1 |page=168 |pmid=21423403 |doi=10.3389/fphys.2010.00168 |pmc=3059938 |type=Review |doi-access=free }}</ref><ref name="AndohTsujikawa2003">{{cite journal |author=Andoh A. |author2=Tsujikawa T. |author3=Fujiyama Y. |title=Role of dietary fiber and short-chain fatty acids in the colon |journal=Curr. Pharm. Des. |year=2003 |volume=9 |issue=4 |pages=347–58 |pmid=12570825 |type=Review |doi=10.2174/1381612033391973 }} </ref>

Due to the body's limited ability to process fructans, inulin has minimal increasing impact on [[blood sugar]], and may potentially have use in managing blood sugar-related illnesses, such as [[metabolic syndrome]].<ref name="liu">{{cite journal |pmid=27623982 |year=2017 |last1=Liu |first1=F. |title=Effect of inulin-type fructans on blood lipid profile and glucose level: A systematic review and meta-analysis of randomized controlled trials |journal=European Journal of Clinical Nutrition |volume=71 |issue=1 |pages=9–20 |last2=Prabhakar |first2=M. |last3=Ju |first3=J. |last4=Long |first4=H. |last5=Zhou |first5=H. W. |doi=10.1038/ejcn.2016.156|s2cid=13767136 }}</ref>

===Medical===
Inulin and its analog [[sinistrin]] are used to help measure kidney function by determining the glomerular filtration rate (GFR), which is the volume of fluid filtered from the renal (kidney) [[Glomerulus (kidney)|glomerular]] capillaries into the [[Bowman's capsule]] per unit time.<ref>{{cite book |title=Essentials of Human Physiology |first=Thomas M. |last=Nosek |chapter=Section 7, Chapter 4, Glomerular Filtration Rate |chapter-url=http://humanphysiology.tuars.com/program/section7/7ch04/7ch04p11.htm |archive-url=https://web.archive.org/web/20160324124828/http://humanphysiology.tuars.com/program/section7/7ch04/7ch04p11.htm |archive-date=2016-03-24 }}</ref>

While inulin is the gold standard for measuring the GFR, it is rarely used in practice due to the expense and difficulty in conducting the test; it requires [[intravenous]] (IV) access for the infusion of inulin as well as up to twelve blood samples taken from the patient over the course of four hours.<ref>{{Citation|last=Langlois|first=Valerie|title=CHAPTER 2 - Laboratory Evaluation at Different Ages|date=2008-01-01|url=https://www.sciencedirect.com/science/article/pii/B9780323048835500088|work=Comprehensive Pediatric Nephrology|pages=39–54|editor-last=Geary|editor-first=Denis F.|place=Philadelphia|publisher=Mosby|language=en|doi=10.1016/b978-0-323-04883-5.50008-8|isbn=978-0-323-04883-5|access-date=2022-02-11|editor2-last=Schaefer|editor2-first=Franz|url-access=subscription}}</ref> To determine the glomerular filtration rate in humans, a large initial dose of inulin is injected, which is followed by a constant infusion of inulin at a rate which compensates for its loss in the urine, thus maintaining a reasonably constant level in the plasma.<ref>{{Cite book |last=Wright |first=Samson |title=Samson Wright's applied physiology |date=1972 |publisher=English Language Book Society, and Oxford University Press |others=Cyril Arthur Keele, Neil Eric |isbn=0-19-263321-X |edition=12th |location=London |oclc=396722036}}</ref>{{rp|228}} In the United States, [[creatinine]] clearance is more widely used to estimate GFR.<ref>{{Cite journal|last1=Joffe|first1=Marshall|last2=Hsu|first2=Chi-yuan|last3=Feldman|first3=Harold I.|last4=Weir|first4=Matthew|last5=Landis|first5=J.R.|last6=Hamm|first6=L. Lee|date=2010|title=Variability of Creatinine Measurements in Clinical Laboratories: Results from the CRIC Study|url=https://www.karger.com/Article/FullText/296250|journal=American Journal of Nephrology|language=en|volume=31|issue=5|pages=426–434|doi=10.1159/000296250|issn=1421-9670|pmc=2883847|pmid=20389058}}</ref>

A 2017 [[systematic review]] of low-to-moderate quality [[clinical trial]] research showed that [[dietary supplement|dietary supplementation]] with inulin-type [[fructans]] reduced blood levels of [[low-density cholesterol]], a [[biomarker]] of [[cardiovascular disease]].<ref name=liu/>

===Possible side effects===
In doses of 15–50 grams per day, dietary inulin increases the frequency of [[defecation]].<ref name="mys">{{cite journal |vauthors=Mysonhimer AR, Holscher HD |title=Gastrointestinal effects and tolerance of nondigestible carbohydrate consumption |journal=Advances in Nutrition |volume=13 |issue=6 |pages=2237–2276 |date=December 2022 |pmid=36041173 |pmc=9776669 |doi=10.1093/advances/nmac094}}</ref> Possible side effects of regularly using inulin in the diet include gastrointestinal discomfort, [[bloating]], [[flatulence]], [[diarrhea]], and stomach inflammation in people with [[allergies]] to inulin.<ref name=mys/><ref>{{cite journal | last1 = Coussement | first1 = Paul A. A. | year = 1999 | title = Inulin and oligofructose: safe intakes and legal status | journal = The Journal of Nutrition | volume = 129 | issue = 7| pages = 1412S–1417S | doi = 10.1093/jn/129.7.1412S | pmid = 10395609 | doi-access = free }}</ref><ref>{{cite journal |title=Inulin fibre promotes microbiota-derived bile acids and type 2 inflammation | doi=10.1038/s41586-022-05380-y |volume=611|journal=Nature |pages=578–584 |year=2022| last1 = Arifuzzaman| first1 =Mohammad| issue=7936 | pmid=36323778 | bibcode=2022Natur.611..578A | s2cid=253266833 | pmc=10576985 }}</ref>

===Industrial use===
Nonhydrolyzed inulin can also be directly converted to [[ethanol]] in a simultaneous [[saccharification]] and fermentation process, which may have potential for converting crops high in inulin into ethanol for fuel.<ref>{{cite journal |author1=Kazuyoshi Ohta |author2=Shigeyuki Hamada |author3=Toyohiko Nakamura |title=Production of High Concentrations of Ethanol from Inulin by Simultaneous Saccharification and Fermentation Using ''Aspergillus niger'' and ''Saccharomyces cerevisiae'' |journal=Applied and Environmental Microbiology |volume=59 |issue=3 |pages=729–733 |year=1992 |doi=10.1128/AEM.59.3.729-733.1993 |pmid=8481000 |pmc=202182}}</ref>

==Biochemistry==
{{More citations needed section|date=February 2021}}
Inulins are [[polymer]]s composed mainly of fructose units ([[Fructan|fructans]]), and typically have a terminal [[glucose]]. The fructose units in inulins are joined by a β(2→1) [[glycosidic bond]]. The molecule is almost exclusively linear, with only a few percent branching.<ref name=":0">{{Cite book |last1=Kays |first1=Stanley J. |url=https://books.google.com/books?id=XwZJN1HSajcC&pg=PA58 |title=Biology and Chemistry of Jerusalem Artichoke: Helianthus tuberosus L. |last2=Nottingham |first2=Stephen F. |date=2007-08-13 |publisher=CRC Press |isbn=978-1-4200-4496-6 |language=en}}</ref>{{rp|58}} In general, plant inulins contain between 2 and 70 fructose units<ref name=":0" />{{rp|58}} or sometimes as high as 200,<ref name=":1">{{Cite book |last1=Rauter |first1=Amélia P. |url=https://books.google.com/books?id=u4RWrMh8JR0C&pg=PA17 |title=Carbohydrates in Sustainable Development I |last2=Vogel |first2=Pierre |last3=Queneau |first3=Yves |date=2010-09-20 |publisher=Springer Science & Business Media |isbn=978-3-642-14836-1 |language=en}}</ref>{{rp|17}} but molecules with less than 10 units are called fructo-oligosaccharides, the simplest being 1-[[trisaccharide|kestose]], which has two fructose units and one glucose unit. Bacterial inulin is more highly branched (more than 15% branching) and contains on the order of tens or hundreds of subunits.<ref name=":1" />{{rp|17}}

Inulins are  named in the following manner, where '''n''' is the number of fructose residues and '''py''' is the abbreviation for [[pyranose|pyranosyl]]:
* Inulins ''with'' a terminal glucose are known as ''alpha''-D-glucopyranosyl-[beta-D-fructofuranosyl](n-1)-D-fructofuranosides, abbreviated as '''GpyFn'''.
* Inulins ''without'' glucose are ''beta''-D-fructopyranosyl-[D-fructofuranosyl](n-1)-D-fructofuranosides, abbreviated as '''FpyFn'''.

Hydrolysis of inulins may yield fructo-oligosaccharides, which are oligomers with a [[degree of polymerization]] (DP) of 10 or less.

==Calculation of glomerular filtration rate==
Inulin is uniquely treated by [[nephrons]] in that it is completely filtered at the [[Glomerulus (kidney)|glomerulus]] but neither secreted nor reabsorbed by the tubules.  This property of inulin allows the [[Clearance (medicine)|clearance]] of inulin to be used clinically as a highly accurate measure of glomerular filtration rate (GFR) — the rate of plasma from the [[afferent arteriole]] that is filtered into Bowman's capsule measured in ml/min.{{Cn|date=March 2021}}

It is informative to contrast the properties of inulin with those of [[para-aminohippuric acid]] (PAH).  PAH is partially filtered from plasma at the glomerulus and not reabsorbed by the tubules, in a manner identical to inulin.  PAH is different from inulin in that the fraction of PAH that bypasses the glomerulus and enters the nephron's tubular cells (via the [[peritubular capillaries]]) is completely secreted.  Renal clearance of PAH is thus useful in calculation of renal plasma flow (RPF), which empirically is (1-[[hematocrit]]) times [[renal blood flow]].  Of note, the clearance of PAH is reflective only of RPF to portions of the kidney that deal with urine formation, and, thus, underestimates the actual RPF by about 10%.<ref>Costanzo, Linda.  Physiology, 4th Edition.  Philadelphia: Lippincott Williams and Wilkins, 2007.  Pages 156–160.</ref>

The measurement of GFR by inulin or sinistrin is still considered the [[Gold standard (test)|gold standard]].  However, it has now been largely replaced by other, simpler measures that are approximations of GFR.  These measures, which involve clearance of such substrates as [[EDTA]], [[iohexol]], [[cystatin C]], [[125I|<sup>125</sup>I]]-[[iothalamate]] (sodium radioiothalamate), the chromium radioisotope [[chromium-51|<sup>51</sup>Cr]] (chelated with EDTA), and [[creatinine]], have had their utility confirmed in large cohorts of patients with chronic kidney disease.{{Cn|date=March 2021}}

For both inulin and creatinine, the calculations involve concentrations in the urine and in the serum. However, unlike creatinine, inulin is not naturally present in the body. This is an advantage of inulin (because the amount infused will be known) and a disadvantage (because an infusion is necessary).{{Cn|date=March 2021}}

==Metabolism ''in vivo''==
Inulin is indigestible by the human [[enzyme]]s [[ptyalin]] and [[amylase]] which are adapted to digest starch and as a result, it passes through much of the [[digestive system]] intact. Only in the [[colon (anatomy)|colon]] do bacteria [[metabolism|metabolise]] inulin with the release of significant quantities of [[carbon dioxide]], [[hydrogen]], and/or [[methane]]. Inulin-containing foods can be rather gassy, especially for those unaccustomed to inulin and these foods should be consumed in moderation at first.{{citation needed|date=November 2019}}

Inulin is a soluble fiber, one of three types of dietary fiber including [[soluble fiber|soluble]], [[insoluble fiber|insoluble]] and [[resistant starch]]. Soluble fiber dissolves in water to form a gelatinous material. Some soluble fibers may help lower blood cholesterol and glucose levels.<ref>{{cite journal |last1=McRorie |first1=Johnson W. |last2=McKeown |first2=Nicola M. |title=Understanding the Physics of Functional Fibers in the Gastrointestinal Tract: An Evidence-Based Approach to Resolving Enduring Misconceptions about Insoluble and Soluble Fiber |journal=Journal of the Academy of Nutrition and Dietetics |date=1 February 2017 |volume=117 |issue=2 |pages=251–264 |doi=10.1016/j.jand.2016.09.021|pmid=27863994 |doi-access=free }}</ref>

Because normal [[digestion]] does not break inulin down into [[monosaccharide]]s, it does not elevate blood sugar levels and may therefore be helpful in the management of diabetes. Inulin also stimulates the growth of bacteria in the [[Gut (zoology)|gut]].<ref name=I1 />
Inulin passes through the [[stomach]] and [[duodenum]] undigested and is highly available to the gut [[bacterial flora]]. This makes it similar to resistant starches and other fermentable carbohydrates.{{Cn|date=March 2021}}

Some traditional diets contain over 20g per day of inulin or fructo-oligosaccharides. The diet of the prehistoric hunter-forager in the Chihuahuan Desert has been estimated to include 135 g per day of inulin-type fructans.<ref>{{cite journal | journal = Br. J. Nutr. | volume = 103 | issue = 11 | pages = 1558–61 | year = 2010 | pmid = 20416127 | doi = 10.1017/S0007114510000966 | author-link1=Jeff D. Leach |last1 = Leach | first1 = J. D. | last2 = Sobolik | first2 = K. D. | title = High dietary intake of prebiotic inulin-type fructans in the prehistoric Chihuahuan Desert | doi-access = free }}</ref>  Many foods naturally high in inulin or fructo-oligosaccharides such as chicory, garlic, and [[leek]] have been seen as "stimulants of good health" for centuries.<ref>{{cite journal | author = Coussement P. | title = Inulin and oligofructose: safe intakes and legal status | journal = J. Nutr. | volume = 129 | issue = 7 Suppl | pages = 1412S–1417S | year = 1999 | pmid = 10395609| doi = 10.1093/jn/129.7.1412S | doi-access = free |url=http://jn.nutrition.org/cgi/content/full/129/7/1412S#SEC1}}</ref>

As of 2013, no regulatory authority had permitted health claims in the marketing of prebiotics as a class.  Inulin's health effects had been studied in small clinical trials which showed that it causes gastrointestinal adverse effects such as bloating and flatulence and it does not affect [[Triglyceride|triglyceride levels]] or development of [[fatty liver]]. It may also help to prevent [[travelers' diarrhea]] and may help increase calcium absorption in adolescents.<ref name=slavin/>

==Natural sources==
{{unreferenced-section|date=May 2025}}
Plants that contain high concentrations of inulin include:
* [[Agave]] (''Agave'' spp.)
* [[Banana]] and [[Cooking plantain|plantain]] ([[Musaceae]])
* [[Burdock]] (''Arctium lappa'')
* [[Camassia|Camas]] (''Camassia'' spp.)
* [[Chicory]] (''Cichorium intybus'')
* [[Echinacea|Coneflower]] (''[[Echinacea]]'' spp.)
* [[Costus]] (''Saussurea lappa'') 
* [[Dandelion]] (''Taraxacum officinale'')
* [[Elecampane]] (''Inula helenium'')
* [[Garlic]] (''Allium sativum'')
* [[Globe artichoke]] (''Cynara scolymus'', ''Cynara cardunculus'' var. ''scolymus'')
* [[Jerusalem artichoke]] (''Helianthus tuberosus'')
* [[Jicama]] (''Pachyrhizus erosus'')
* [[Leopard's bane]] (''[[Arnica montana]]'')
* [[Mugwort]] root (''[[Artemisia vulgaris]]'')
* [[Onion]] (''Allium cepa'')
* [[Wild yam]] (''[[Dioscorea]]'' spp.)
* ''[[Yacón]]'' (''Smallanthus sonchifolius'')

==References==
{{Reflist|2}}

{{carbohydrates}}

[[Category:Polysaccharides]]
[[Category:Food additives]]
[[Category:Prebiotics (nutrition)]]
[[Category:Fructosides]]