Acceptability of a new modular protein substitute for the dietary treatment of phenylketonuria

The major source of protein in the dietary treatment of phenylketonuria (PKU) is a phenylalanine-free amino acid mixture. Traditionally, these medical products have also contained other nutrients and have been in powder form. However, their disagreeable taste and odour, the large volume required to provide sufficient protein and the inconvenience of their preparation and storage have hindered compliance with consumption among adolescents and adults. We studied the acceptability of a new medical product for the treatment of PKU. This product, Phlexy-10 (SHS North America, Gaithersburg, MD, USA), is available in three forms: sachets of premeasured powder to be constituted as a drink, fruit-flavoured bars and prefilled capsules. A vitamin-mineral mixture is separately provided. The forms are interchangeable because each component (one sachet, one bar or 20 capsules) provides 10 g of amino acids. Since the product is primarily a source of amino acids, protein requirements can be met using a smaller volume than with traditional medical products. Eleven subjects enrolled in a 24-week trial that included clinical and laboratory evaluations. Nine subjects completed the study and 8 remained on the Phlexy-10 after the study. The powder drink was the favourite module used. One-third of the subjects included the bars and another third included the capsules in their regimens. The vitamin-mineral mixture was the least acceptable component. Mean weekly blood phenylalanine decreased by 40% from mean baseline levels. Blood concentrations of vitamins and minerals were normal except for a low zinc concentration in two subjects and a low vitamin B(1)2 concentration in another. The lower caloric content and the separate vitamin-mineral mixture require careful monitoring of these nutrients. Phlexy-10 appears to be an adequate medical product for the treatment of PKU. Its convenience, flexibility of form and improved taste are appealing to many individuals on diet for PKU.