Introduction:
A phenylalanine-restricted diet based on phenylalanine-free amino acid supplement and special low-protein food products with limited phenylalanine (Phe) content is the main treatment method in classical phenylketonuria (PKU). High diet costs are one of the common daily difficulties reported by patients and their caregivers.

Aim of the study:
The aim of this study was to compare 24-hour model meal plans and their costs, considering PKU children at different stages of development, with restriction-free diets of their peers.

Material and Methods:
Model meal plans were used for cost analysis; however, the disease-imposed constraints made the task of creating similar types of menus very challenging.

Results:
Meal plans for PKU children, which included specialised low-protein foods, were on average 41.49% more expensive than a traditional balanced diet for healthy children. The lowest cost difference was found in the menu for a 17-year-old child and the highest in the meal plan for a 10-year-old girl – 30.05% and 51.57%, respectively. The difference in the cost of the diet for a three-year-old was 42.85%. Results of the analysis demonstrate that following PKU dietary recommendations in order to maintain blood Phe concentration at the appropriate level generates a noticeable financial burden for patients and their caregivers.

Conclusions:
It is necessary to undertake an in-depth analysis of the costs of the therapeutic strategy used in PKU and consider the possibility of reimbursement of low-protein foods.