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.