The Simplified Diet for PKU: Practices of Swedish Metabolic Dietitians

Background: Dietary management of phenylketonuria (PKU) focuses on restricting phenylalanine (Phe) intake. The European PKU guidelines and the PKU Dietary Handbook recommend a simplified PKU diet, allowing unrestricted consumption of many low-Phe foods, called free foods. While this approach may reduce the treatment burden for patients, its implementation varies. This study investigated practices of Swedish metabolic dietitians regarding the simplified diet and the use of free foods for classical PKU (cPKU) and compared these with European recommendations. Methods: A survey was distributed to all metabolic dietitians in Sweden. The survey included questions on professional experience, the use of free foods and the classification of 135 low-protein food items as never, sometimes or always counted in cPKU. Data were summarised descriptively. Results: All 13 eligible dietitians participated. The use of free foods was recommended by 8/13 dietitians. Of foods classified as free in the PKU Handbook, about one third were commonly restricted in Swedish PKU practice. For 39% of the foods surveyed, no single response option (never, sometimes or always counted) reached >50%, indicating variation in practice. Classification of individual foods partially aligned with their Phe content, but portion size and concerns about excessive Phe intake also influenced advice. Conclusions: Significant variation exists in the dietary management of PKU in Sweden, and the simplified diet approach is not consistently implemented. Dietitians' concerns about the safety of increased Phe intake from free foods play a central role in this. These findings highlight challenges in incorporating international guidelines into national practice and underscore the need for further research to address dietitians' safety concerns related to the simplified diet.