Use of Glycomacropeptides in Medical Nutrition Therapy of Phenylketonuria Patients

Abstract

Phenylketonuria (PKU) is a disease in which phenylalanine in the blood rises due to deficiency of the enzyme phenylalanine hydroxylase. Patients are prevented from increasing phenylalanine levels in the blood by applying a phenylalanine-restricted diet. In phenylalanine-restricted diet treatment, proteins, which are natural sources of phenylalanine, are removed from the diet. Amino acid-based protein substitutes that do not contain phenylalanine are added to the diet to meet the patient’s protein needs. However, the taste of these protein substitutes is often disliked. For this reason, studies have been conducted on alternative protein substitutes. Glycomacropeptide (GMP), a natural whey-based protein, is considered as an alternative protein substitute because it contains residual amounts of phenylalanine. The aim of this review is to evaluate studies examining the role of GMP in the management of PKU. Studies have shown that the entire need for protein replacement should not be met with GMP-based protein substitutes and that a certain amount of amino acid-based protein substitutes that do not contain phenylalanine should be included in the diet, that the phenylalanine contained in GMP is risky in pediatric PKU patients, that it can be used in children but that the amount of phenylalanine coming from GMP should be deducted from the daily phenylalanine intake, and that GMP suppresses appetite. It was concluded that it has a good taste and that more studies are needed to determine its effects on blood phenylalanine and tyrosine levels, microbiota and bone health.