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Galacto-oligosaccharides (GOS)

What are galacto-oligosaccharides (GOS)?

Galacto-oligosaccharides (galacto from galactose; oligo = few; saccharide = sugar) or GOS are composed of galactose molecules with one glucose on the end, altogether containing 3-8 simple sugars. GOS cannot be digested in the human small intestine, so it travels unchanged into the large intestine, where beneficial colonic bacteria break them down into gases and short-chain fatty acids (SCFAs), which can be absorbed and used by the body ^[1].

Galacto-oligosaccharides are similar to human milk oligosaccharides (HMO) ^[3].

GOS Sources

Semi-synthetic GOS can be produced from lactose ^[1]. GOS (up to about 5 g/100 g) can be added as a soluble fiber to infant formula, powdered milk, biscuits, dairy products, fruit drinks, confectionery, cereal bars or other commercial foods.

GOS Supplements

GOS may be included in some prebiotic and soluble fiber supplements.

Possible GOS Benefits

GOS promote the growth of beneficial Bifidobacteria in the large intestine ^[3]but are, according to Journal of Nutrition, currently not considered prebiotics ^[2].
GOS act as a soluble dietary fiber, which may soften the stool and increase the frequency of bowel movements ^[3].

GOS Safety and Side Effects

GOS is currently not yet Generally Recognized As Safe by the US Food and Drug Administration (FDA) ^[1].

GOS in amounts 12 g per day or lower is usually well tolerated. Larger amounts may cause abdominal bloating, excessive gas (flatulence) or other mild gastrointestinal symptoms ^[3].

Related Nutrients

GRAS Notification US Food and Drug Administration
Roberfroid, M., 2007, Prebiotics: the concept revisited The Journal of Nutrition
Niittnyen L et al, 2007, Galacto-oligosaccharides and bowel function PubMed Central