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Galacto-oligosaccharides (GOS) ; Fuel for Health

Down in the colon there are trillions of microbes patiently waiting for scraps of of what we eat each day.

They wait for fragments of carbohydrates, resistant starches, and dietary fiber to arrive so that can fuel their own replication and produce metabolites such as short chain fatty acid (known as a post biotic).


What conundrum it must be if we aren't eating foods that fuel our microbiome!


The colon is like a bioreactor designed provide an effective environment to transform biochemicals (prebiotics) into products (postbiotics).

Prebiotics are generally oligomers made up of 4 to 10 monomeric hexose unit (technically a non-absorbable sugar). They actually taste sweet.



A detailed guideline for probiotics and prebiotics has been published by the World Gastroenterology Organization.


In order to be a classified as a prebiotic; the compound must meet four criteria:


· It cannot be hydrolyzed nor absorbed in the small intestine. Meaning they are not processed until the colon.

· It must be a selective substrate for beneficial commensals in the large intestine. Meaning that commensal bacteria of the large intestine use the prebiotic as fuel source.

· It must change colonic microflora toward healthier composition

· It must induce luminal changes benefiting host.


If something is called a prebiotic but does meet these four criteria they are technically not a prebiotic.


Prebiotics have many benefits but mainly they help boost commensal microbes who as a result suppress the growth of pathogenic bacteria and protect against pathogen invasion.



from: Megur A, Daliri EB-M, Baltriukienė D, Burokas A. Prebiotics as a Tool for the Prevention and Treatment of Obesity and Diabetes: Classification and Ability to Modulate the Gut Microbiota. International Journal of Molecular Sciences. 2022; 23(11):6097. https://doi.org/10.3390/ijms23116097


Prebiotics are linked to reduced disease process ( lower colorectal cancer risk, lower heart disease, reduced risk of Crohn's Diseases, reduced risk of IBS, reduced risk of atopic dermatitis) and improved brain and immune health



from: Davani-Davari D, Negahdaripour M, Karimzadeh I, Seifan M, Mohkam M, Masoumi SJ, Berenjian A, Ghasemi Y. Prebiotics: Definition, Types, Sources, Mechanisms, and Clinical Applications. Foods. 2019 Mar 9;8(3):92. doi: 10.3390/foods8030092. PMID: 30857316; PMCID: PMC6463098.


The main prebiotics are Fructooligosaccharides (FOS), Galacto-oligosaccharides (GOS), Pectin, Inulin, Resistant Starch, Xylooligosaccharides (XOS), and Fucoidan.


Galacto-oligosaccharides (GOS) are short-chain complex carbohydrates composed of several (usually three to nine) galactose molecules linked together with alpha-1,6 glycosidic bonds. The most common type of GOS contains three galactose molecules, also known as tri-galactosyl-oligosaccharide or oligogalactose .


This is not to be confused with the term Oligosaccharide which is a term that describes a category of foods that contain carbohydrate chain made up of three to 10 simple sugars.

So Galacto-oligosaccharides are a type of oligosaccharide but do not represent the whole category. While Oligosaccharides consist of many healthy foods; only one other type of oligosaccharides (Fructooligosaccharides) are considered prebiotics.


There are two forms of Galacto-oligosaccharides... alpha-GOS (α-linked galactosyl sucrose derivates) and βeta- linked lactose-derived GOS . Alpha-gos is found in pulses and legumes whereas Beta-GOS is found in Human's Milk and Cow's Milk.


The key difference between B-GOS and alpha-GOS is the type of linkage between the galactose molecules in their structure. In B-GOS, the galactose molecules are linked by a beta (β) linkage, while in alpha-GOS, they are linked by an alpha (α) linkage.


This difference in linkage changes which bacteria will consume these prebiotics.


It seems that Bifidobacteria can grow from B-GOS may be more effective at stimulating the growth of Bifidobacteria species. Yet-alpha Gos will stimulate both of both Bifidobacterium and Lactobacillus, another type of beneficial bacteria. Some research has also showed that alpha-gos can decrease possible pathogens bacteroides, clostridium histolyticum, Escherichia coli, Desulfovibrio spp (UC/H2s)


Beta-linked Galacto-Oligosaccharides are even being produced as a supplement so they can be added to infant formula or consumed for health reasons. The Bimuno brand -Beta-GOS is featured in many supplements. But because it comes from dairy it may not be well tolerated in those with dairy intolerance.





Alpha- linked Galacto-Oligosaccharides are found in large amounts in the following foods:

  • Beet roots

  • Black beans

  • Bran-wheat bran

  • Bran cereal

  • Mixed-grain breakfast cereals

  • Whole grain cereals

  • Butter beans

  • Butternut Squash

  • Pumpkin

  • Cashews,

  • Chickpeas

  • Green peas

  • Haricot beans

  • Lentils-green

  • Lentils-red

  • Lima-beans

  • Muesli

  • Mung beans

  • Pinto beans

  • Pistachios

  • Quick oats

  • Red kidney beans

  • Rye

  • Soybeans

  • Spelt

  • Split peas

  • White beans

  • Whole wheat

Also found in certain prebiotic supplements: Such as Poly-prebiotic by Pure Encapsulations





As a supplement,there are a wide range of therapeutic uses so your individual dosing should be discussed with a licensed health care provider. However, they can be helpful for constipation, IBS, Atopic Dermatitis, to improve calcium absorption, to address metabolic syndrome, and to prevent gut infections.


Please note: when you add these foods and/or supplements into your regimen you will likely have temporary side effects of abdominal bloating and flatulence that will diminish with time.


So start gradual and build up.



Interested in this topic:


Listen to:

Fiber and Colonic Inflammation Minding your Microbiota with Andrea Hardy, RD Intestinal Barrier and Permeability with Lucy Mailing Phd


Read about my gastrointestinal health approaches here


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