The invention relates to a composition comprising) (i) one or more ω-3 fatty acids selected from the group consisting of DHA, DPA and EPA and (ii) one or more pyrimidine derivatives selected from the group consisting of uridine sources and cytidine sources for use in decreasing or normalizing the phenyl alanine level in the blood of a PKU patient or for use in dietary management of phenylalanine levels in the blood of a PKU patient.
