What It Is and How It's Made
GOS is produced from lactose using an enzyme (beta-galactosidase) that, instead of simply breaking lactose down into its two component sugars, rearranges some of it into longer chains: galactose units linked together, usually ending in a glucose unit. The starting material is lactose, typically derived from milk, processed through this enzymatic step into a non-digestible oligosaccharide.
How It Differs From Inulin and FOS
Inulin and FOS are fructans, chains built from fructose. GOS is built from galactose, a different sugar with a different chemical structure, even though all three end up classified as soluble, fermentable fibre with broadly similar roles in food. The fact that GOS starts from lactose is also a practical difference worth knowing: unlike plant-derived fructans, GOS production begins with a dairy-derived raw material, which matters for anyone checking a label for dairy-free or vegan suitability, even though the finished GOS ingredient itself is not lactose.
How It's Classified as Dietary Fibre
GOS meets the Food Standards Code's dietary fibre definition on the same structural and digestion-resistance grounds as other recognised oligosaccharides. It's commonly used in infant formula as well as general food and supplement applications, reflecting a long history of safety assessment in that context specifically.
FODMAP Status
GOS is a galacto-oligosaccharide, one of the specific carbohydrate groups the FODMAP framework measures directly (the "O" in FODMAP covers both fructans and galacto-oligosaccharides), so it's high FODMAP by definition in the same way inulin and FOS are. See which fibre supplements are low FODMAP for how this compares to other ingredients.
Sources
- Australia New Zealand Food Standards Code, Standard 1.2.8, Nutrition Information Requirements
- NHMRC, Nutrient Reference Values for Australia and New Zealand: Dietary Fibre