- Galactooligosaccharides (GOS) are non-digestible carbohydrates belonging to the family of prebiotic oligosaccharides. They are typically composed of 2–8 galactose residues linked to a terminal glucose unit, connected by β-(1→3), β-(1→4), or β-(1→6) glycosidic bonds. Their structural diversity arises from the specific enzymatic processes used to produce them, which involve the action of β-galactosidase on lactose. Because humans lack the enzymes required to hydrolyze these β-glycosidic linkages in the small intestine, GOS resist digestion and pass intact to the colon, where they serve as fermentable substrates for gut microbiota.
- In the intestinal environment, GOS exert their primary function as prebiotics, selectively stimulating the growth and activity of beneficial bacterial genera such as Bifidobacterium and Lactobacillus. Fermentation of GOS leads to the production of short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate, which lower colonic pH, inhibit pathogenic bacteria, and provide metabolic benefits to the host. This modulation of the microbiota contributes to improved digestion, enhanced immune function, and protection against intestinal infections. Additionally, GOS may indirectly influence systemic processes such as lipid metabolism, glucose regulation, and even brain function through the gut–microbiota–brain axis.
- In infant nutrition, GOS are of particular importance. Human milk naturally contains a wide variety of oligosaccharides (human milk oligosaccharides, HMOs), which play a central role in shaping the infant gut microbiome. Because synthesizing HMOs on a commercial scale is challenging, GOS are commonly added to infant formulas as functional substitutes. They help mimic some of the beneficial effects of HMOs, including fostering a bifidobacteria-rich microbiota, enhancing gut barrier function, and supporting immune development.
- In the food and nutraceutical industries, GOS are widely used as functional ingredients due to their stability, solubility, and mild sweetness (about 20–40% of sucrose). They are incorporated into dairy products, beverages, baked goods, and dietary supplements aimed at improving gut health. Their ability to tolerate heat and acidic conditions also makes them suitable for processing in a variety of foods without losing functionality. Beyond food, GOS have been explored for potential use in animal feed, where they can promote gut health and reduce reliance on antibiotics in livestock.
- Emerging research suggests that GOS may have additional physiological benefits beyond gut health. These include modulation of immune responses, reduction of allergy risk in infants, enhancement of calcium absorption and bone health, and potential influences on mental well-being via gut–brain communication. Their safety and tolerance are generally high, though excessive consumption may cause mild gastrointestinal discomfort in sensitive individuals.
