Abstract: The invention pertains to the use of a composition in the manufacture of a productor method for therapeutically improving, promoting, restoring or maintaining white matter integrity in a subject suffering from PKU and/or in a subject suffering from or at increased risk of impaired white matter integrity associated with PKU, said composition comprising therapeutic amounts of at least one ?-3 polyunsaturated fatty acid (LCPUFA) selected from the group consisting of docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA); and one of more of uridine, cytidine and/or an equivalent thereof, including salts, phosphates, acyl derivatives and/or esters. The invention also pertains to a composition for use in such use or method.