Phenylketonuria is currently treated by a special diet to avoid elevated blood concentration of the essential amino acid phenylalanine. The authors examined 20 phenylketonuric children in the Inborn Error of Metabolism Department of Institute of Child Health in Athens. The children had simultaneous clinical and laboratory investigations. Blood cholesterol levels of these children were low in comparison with the levels of healthy children of the same age, but the triglyceride levels were higher as a result of a special diet containing a large amount of carbohydrates. Because of the triglyceride elevation the authors recommend supplementary vegetable fat intake, such as in olive oil, for their patients' dietary control.

Although total, free and esterified carnitine blood levels were found to be low (p less than 0.001) in phenylketonuric patients under dietary treatment compared to controls, no clinical signs of carnitine deficiency were noticed. Exclusion from the PKU diet of nutrients rich in carnitine has been suggested. Supplementation of the diets with carnitine or preferably enrichment of the PKU formulas with carnitine will rectify the restriction of extrinsic carnitine in PKU dietary treatment.