THE PRESENT INVENTION RELATES TO A NUTRITIONAL COMPOSITION COMPRISING AT LEAST TWO DIFFERENT BETA-GALACTO-OLIGOSACCHARIDES (BGOS) A AND B WHEREIN THE MAJORITY OF LINKAGES BETWEEN TWO GALACTOSE RESIDUES IN BGOS A ARE BETA 1,4 AND/OR BETA 1,6, AND THE MAJORITY OF LINKAGES BETWEEN TWO GALACTOSE RESIDUES IN BGOS B ARE BETA 1,3. SUCH MIXTURES SHOW SUPERIOR EFFECTS ON THE IMMUNE SYSTEM AND ARE PARTICULARLY SUITABLE FOR INFANT NUTRITION.