GOS (galactooligosaccharides) are a mixture of oligosaccharides constituted by glucose and galactose moyeties through a trans-glycosylation reaction performed industrially with beta-galactosidase enzyme from A. niger, on a substrate of lactose from dairy origin.
As for what happens with FOS, human gastrointestinal tract does not produce enzymes capable of hydrolyzing GOS, that pass unmodified stomach (except for tiny amounts that undergo acid hydrolysis) and guts and arrive in the colon where they are fermented by resident flora to SCFA (short chain fatty acids); these small molecules serve particularly as trophic factors for gut epithelial cells, also stabilizing phyisiology and function of this organ, and are also used as auxiliary “fuel” by the organism. Resident microbiota results boosted and enriched in biofidobacterial population.
Daily suggested dosage is g, up to 10g/day in different servings. GOS are also used to complement probiotic formulations (synbiotic) and infant formulas.