galactooligosaccharides

Galactooligosaccharides (GOS) are a class of nondigestible oligosaccharides composed predominantly of galactose units linked by β-glycosidic bonds, usually with a glucose unit at the reducing end. Their degree of polymerization generally ranges from about 2 to 8. Commercial GOS are typically produced by transgalactosylation of lactose using β-galactosidase enzymes and are added to foods and dietary supplements as prebiotic ingredients. Trace amounts of GOS can occur naturally in human milk and some dairy products, but industrially produced GOS provide standardized prebiotic activity.

In the gut, GOS resist digestion in the upper gastrointestinal tract and are fermented by the colon’s microbiota. They preferentially promote growth of beneficial bacteria such as bifidobacteria, with lactobacilli also contributing to fermentation. This bifidogenic effect is associated with the production of short-chain fatty acids and can influence gut motility and microbial balance. Health outcomes studied include improvements in stool frequency and consistency, particularly in constipation, as well as potential but variable effects on mineral absorption and immune markers. Evidence across studies is mixed, and responses can be influenced by the overall diet and individual microbiota.

Safety and regulation: GOS are widely used as a food ingredient and are generally regarded as safe when consumed at typical levels in foods and supplements. Some individuals may experience mild gastrointestinal symptoms, such as gas or bloating, at high intakes. Regulatory status varies by jurisdiction, with many authorities evaluating safety for specific uses and dosage ranges, including use in infant formulas and adult foods.