{{Short description|Class of prebiotics}} {{Chembox <!-- Images --> | ImageFile = Galactooligosaccharide.svg | ImageSize = 200px | ImageAlt = <!-- Names --> | IUPACName = | OtherNames = <!-- Sections --> | Section1 = {{Chembox Identifiers | CASNo = | PubChem = | ChEBI = 24151 | SMILES = }} | Section2 = {{Chembox Properties | Formula = (C<sub>6</sub>H<sub>10</sub>O<sub>5</sub>)<sub>n</sub> | MolarMass = Variable | Appearance = | Density = | MeltingPt = | BoilingPt = | Solubility = }} | Section3 = {{Chembox Hazards | MainHazards = | FlashPt = | AutoignitionPt = }} }}
'''Galactooligosaccharides''' ('''GOS'''), also known as '''oligogalactosyllactose''', '''oligogalactose''', '''oligolactose''' or '''transgalactooligosaccharides''' ('''TOS'''), belong to the group of prebiotics. Prebiotics are defined as non-digestible food ingredients that beneficially affect the host by stimulating the growth and/or activity of beneficial bacteria in the colon. GOS occurs in commercially available products such as food for both infants and adults.
== Chemistry == The composition of the galactooligosaccharide fraction varies in chain length and type of linkage between the monomer units. Galactooligosaccharides are produced through the enzymatic conversion of lactose, a component of bovine milk.
A range of factors come into play when determining the yield, style, and type of GOS produced. These factors include: * enzyme source * enzyme dosage * feeding stock (lactose) concentration * origins of the lactose * process involved (e.g. free or immobilized enzyme) * reaction conditions impacting the processing situation * medium composition
GOS generally comprise a chain of galactose units that arise through consecutive transgalactosylation reactions, with a terminal glucose unit. However, where a terminal galactose unit is indicated, hydrolysis of GOS formed at an earlier stage in the process has occurred. The degree of polymerization of GOS can vary quite markedly, ranging from 2 to 8 monomeric units, depending mainly on the type of the enzyme used and the conversion degree of lactose.
== Digestion research == {{Main|Dietary fiber#Activity in the gut}} {{medical citations needed|section|date=November 2017}} Because of the configuration of their glycosidic bonds, galactooligosaccharides largely resist hydrolysis by salivary and intestinal digestive enzymes.<ref name=ajcn/> Galactooligosaccharides are classified as prebiotics, defined as non-digestible food ingredients as substrate for the host by stimulating the growth and activity of bacteria in the colon.<ref name=ajcn/>
The increased activity of colonic bacteria results in various effects, both directly by the bacteria themselves or indirectly by producing short-chain fatty acids as byproducts via fermentation. Examples of effects are stimulation of immune functions, absorption of essential nutrients, and synthesis of certain vitamins.<ref>{{cite journal |author=Gibson GR |title=Dietary modulation of the human gut microflora using prebiotics |journal=British Journal of Nutrition |volume=80 |issue=4 |pages=S209–12 |date=October 1998 |pmid=9924286 |doi= 10.1017/S0007114500006048|doi-access=free }}</ref><ref>{{cite journal |author=Roberfroid MB |title=Prebiotics and probiotics: are they functional foods? |journal=American Journal of Clinical Nutrition |volume=71 |issue=6 Suppl |pages=1682S–7S; discussion 1688S–90S |date=June 2000 |pmid=10837317 |doi= 10.1093/ajcn/71.6.1682S|doi-access=free }}</ref><ref>{{cite journal |vauthors=Macfarlane GT, Steed H, Macfarlane S |title=Bacterial metabolism and health-related effects of galacto-oligosaccharides and other prebiotics |journal=Journal of Applied Microbiology|volume=104 |issue=2 |pages=305–44 |date=February 2008 |pmid=18215222 |doi=10.1111/j.1365-2672.2007.03520.x |s2cid=205319925 }}</ref>
===Stimulating bacteria=== Galactooligosaccharides are a substrate for bacteria, such as ''Akkermansia muciniphila'', ''Bifidobacteria'' and lactobacilli. Studies with infants and adults have shown that foods or drinks enriched with galactooligosaccharides result in a significant increase in ''Bifidobacteria''.<ref name="ajcn">{{cite journal|pmid=23824724|year=2013|last1=Jeurink|first1=P. V|title=Mechanisms underlying immune effects of dietary oligosaccharides|journal=American Journal of Clinical Nutrition|volume=98|issue=2|pages=572S–7S|last2=Van Esch|first2=B. C|last3=Rijnierse|first3=A|last4=Garssen|first4=J|last5=Knippels|first5=LM|doi=10.3945/ajcn.112.038596|url=http://ajcn.nutrition.org/content/98/2/572S.long|doi-access=free}}</ref> These sugars can be found naturally in human milk, known as human milk oligosaccharides.<ref>{{Cite web|title=Human Milk Oligosaccharides|url=https://www.nestlenutrition-institute.org/resources/hot-topics/details/human-milk-oligosaccharides|access-date=2020-12-04|website=NNI Global Website|language=en|archive-date=2017-09-19|archive-url=https://web.archive.org/web/20170919113052/https://www.nestlenutrition-institute.org/resources/hot-topics/details/human-milk-oligosaccharides|url-status=dead}}</ref> Examples include lacto-''N''-tetraose, lacto-''N''-neotetraose, and lacto-''N''-fucopentaose.<ref>{{Cite book|last=Miesfeld, Roger L.|title=Biochemistry|others=McEvoy, Megan M.|date=July 2017|isbn=978-0-393-61402-2|edition=First|location=New York, NY|oclc=952277065}}</ref>
===Immune response=== Human gut microbiota play a key role in the intestinal immune system.<ref name=ajcn/> Galactooligosaccharides (GOS) support natural defenses of the human body via the gut microflora,<ref>{{cite journal |author1=Gibson G.R. |author2=McCartney A.L. |author3=Rastall R.A. | year = 2005 | title = Prebiotics and resistance to gastrointestinal infections | journal = Br. J. Nutr. | volume = 93 | issue = Suppl. 1| pages = 31–34 |doi=10.1079/BJN20041343 |pmid=15877892 | doi-access = free }}</ref> indirectly by increasing the number of bacteria in the gut and inhibiting the binding or survival of ''Escherichia coli'', ''Salmonella'' ''typhimurium'' and ''Clostridia''.<ref>{{cite journal |author1=Shoaf K. |author2=Muvey G.L. |author3=Armstrong G.D. |author4=Hutkins R.W. | year = 2006 | title = Prebiotic galactooligosaccharides reduce adherence of enteropathogenic Escherichia coli to tissue culture cells | journal = Infect Immun | volume = 74 | issue = 12| pages = 6920–8 | doi=10.1128/iai.01030-06|pmid=16982832 | pmc=1698067}}</ref><ref>{{cite journal |vauthors=Sinclair HR, etal | year = 2009 | title = Galactooligosaccharides (GOS) inhibit Vibrio cholerae toxin binding to its GM1 receptor | journal = Journal of Agricultural and Food Chemistry | volume = 57 | issue = 8| pages = 3113–3119 | doi=10.1021/jf8034786 | pmid=19290638| bibcode = 2009JAFC...57.3113S }}</ref> GOS can positively influence the immune system indirectly through the production of antimicrobial substances, reducing the proliferation of pathogenic bacteria.<ref>{{cite journal |vauthors=Macfarlane GT, Steed H, etal | year = 2008 | title = Bacterial metabolism and health-related effects of galacto-oligosaccharides and other prebiotics | journal = Journal of Applied Microbiology | volume = 104 | issue = 2| pages = 305–344 | doi=10.1111/j.1365-2672.2007.03520.x | pmid=18215222| s2cid = 205319925 }}</ref><ref>{{cite journal |vauthors=Vos AP, M'Rabet L, etal | year = 2007 | title = Immune-modulatory effects and potential working mechanisms of orally applied nondigestible carbohydrates | journal = Critical Reviews in Immunology | volume = 27 | issue = 2| pages = 97–140 | doi=10.1615/critrevimmunol.v27.i2.10| pmid = 17725499 }}</ref>
===Constipation=== Constipation is a potential problem, particularly among infants, the elderly, and pregnant women. In infants, formula feeding may be associated with constipation and hard stools.<ref>{{cite journal|pmc=4188896|year=2014|last1=Scholtens|first1=P. A|title=Stool characteristics of infants receiving short-chain galacto-oligosaccharides and long-chain fructo-oligosaccharides: A review|journal=World Journal of Gastroenterology|volume=20|issue=37|pages=13446–13452|last2=Goossens|first2=D. A|last3=Staiano|first3=A|doi=10.3748/wjg.v20.i37.13446|pmid=25309075 |doi-access=free }}</ref> Galactooligosaccharides may improve stool frequency and relieve symptoms related to constipation.<ref>{{cite journal|pmid=28262216|year=2017|last1=Yu|first1=T|title=Effects of Prebiotics and Synbiotics on Functional Constipation|journal=The American Journal of the Medical Sciences|volume=353|issue=3|pages=282–292|last2=Zheng|first2=Y. P|last3=Tan|first3=J. C|last4=Xiong|first4=W. J|last5=Wang|first5=Y|last6=Lin|first6=L|doi=10.1016/j.amjms.2016.09.014|doi-access=free}}</ref>
==See also== * Xylooligosaccharide (XOS)
==References== {{reflist|2}}
{{Carbohydrates}}
Category:Oligosaccharides Category:Prebiotics (nutrition)