Evaluation of Low Phenylalanine Formulas

Study Design This is a 2-stage, 15-week randomized crossover trial. The randomized crossover design was chosen as it reduces the influence of differences among individuals; and it offers statistical efficiency (requires fewer subjects than non-crossover designs). In summary, 2 groups of 9 participants each will be assigned to either (1) sequence 1: take GMP-AA-based PS for the first 4 weeks and then take only L-AA-based Protein Substitute for 4 weeks, or (2) take only L-AA-based Protein Substitute for the first 4 weeks and then take GMP-AA-based PS for 4 weeks. At the end of the first 4 weeks, a 2-week washout period will follow with both groups only consuming L-AA-based PS. Randomization will be generated by a block randomization system and the random order will be kept within a sealed envelope. Primary research objective The principal research objective of this study is to evaluate the effect on Phe levels of a low-Phe diet combined with a purified GMP-AA-based protein substitute (containing 1 mg Phe/g Protein Equivalent), in the treatment of paediatric patients with PKU. Secondary research objectives The secondary objectives of the study aim to investigate whether there are any differences between the GMP-AA-based protein substitute and L-AA-based protein Substitute in the frequency and quantity of protein substitute intake, if any GI (gastrointestinal) symptoms occur with ingestion of the GMP-AA-based protein substitute, effect on satiety (hunger) and mood and any differences in anthropometric data.