An oligosaccharide ingredient comprising glycosylated amino acids and peptides of the general formula RnSacm where R is an amino acid residue, Sac is a monosaccharide selected from the group comprising N-acetyl-neuraminic acid, N-acetyl galactosamine and galactose, n has a value between 1 and 10 with the proviso that if n has the value 1 R is a threonine residue or a serine residue and if n has a value between 2 and 10 the peptide contains at least one threonine or serine residue, m has a value between 2 and 4 and at least 20 mol % of the ingredient is N-acetyl-neuraminic acid.