Comparison of the protein quality of dietetically treated phenylketonuria patients with the recommendations of the WHO Expert Consultation.

The protein quality of the diets of phenylketonuria (PKU) children of different ages (3 months, 10 months, 3 years, 8 years, 12 years, 16 years) with low or high phenylalanine (Phe) tolerance was assessed according to the recommendations of the FAO/WHO consultation group [13]. The amount of each essential amino acid (AA) per gram dietary protein was calculated and compared to the reference. The resultant amino acid score (AAS) indicated a limited to inadequate biological protein quality of the diets in 3-month-old infants (2.2 g protein/kg body weight/day) and 10-month-old infants (2.0 g protein/kg body weight/day) with a "high" Phe tolerance. In all other age groups the AAS was > 100%. However remarkable imbalances in the AA pattern were apparent. Beginning with the age of 3 years (1.7 g protein/kg body weight/day) the intake of the AA lysine and isoleucine was three or two times higher than recommended. At the age of 8 years (1.4 g protein/kg body weight/day) the intake of three AA (valine, isoleucine, lysine) was-related to the WHO recommendations-217%, 229% and 291%. Similar results could be found in the age groups of 12 years (1.1 g protein/kg body weight/day) and 16 years (0.9 g protein/kg body weight/day), respectively. These calculations might help to reconsider the composition of the AA mixtures used in the dietetic treatment of PKU patients.