In phenylketonuria, compliance and diet is a difficult issue; it is hard to quantify and is under-researched. It is influenced by many factors. Failure to consume prescribed quantity of protein substitute has been commonly reported and is probably affected by their acceptability, format and timing of administration. There are few reports documenting actual phenylalanine intake and blood phenylalanine control, but it is possible that the more rigorous systems for allocation of phenylalanine are associated with worse compliance. The dry, hard and insipid nature of many low protein products may lead to their under usage and consequent boredom and hunger. The diet becomes increasingly harder to maintain as children grow older and seek fewer constraints in their meals.
Conclusion: In phenylketonuria, encouraging adherence to diet requires continual education, reinforcement and support from the family and professionals within the support team.