In children with classical phenylketonuria (PKU), a lifelong low phenylalanine diet is the only treatment option with natural protein (phenylalanine) intake restricted to < 20% of safe recommended intake [1] to minimise neurological damage. The diet must be supplemented with artificial protein or protein substitutes. These are traditionally based on L-amino acids (AA), providing phenylalanine free nitrogen, essential amino acids, tyrosine, vitamins and minerals supporting growth, physiological pathways and protein synthesis. Casein glycomacropeptide (CGMP) is a bioactive sialylated glycophosphopeptide, a derivative fro
