Graduation Date

Spring 5-5-2018

Document Type


Degree Name

Doctor of Philosophy (PhD)


Medical Sciences Interdepartmental Area

First Advisor

William Rizzo, MD


Phenylalanine hydroxylase (PAH) deficiency, commonly known as phenylketonuria (PKU), is an inborn error of metabolism that causes the accumulation of phenylalanine and results in intellectual disability if left untreated. The primary treatment for PKU is a lifelong diet that selectively restricts phenylalanine intake and is aimed at keeping blood phenylalanine in the therapeutic range of 120-360 μmol/L. Qualitative research in PKU is limited, but research has stressed the challenges individuals face in following a diet so different than their peers Previous attempts in Europe and Australia have been successful in allowing free use of certain fruits and vegetables, as well as protein counting. In Nebraska, metabolic control remains optimal among children birth to 12 years; however, suboptimal control attenuates for individuals, ages 13 through adulthood. This study was designed to investigate whether the Simplified Diet would improve metabolic control of PKU in older children and adults. Thirty patients, ranging in age from 13 to 50 years, participated in a study at the University of Nebraska Medical Center and Children’s Hospital and Medical Center in Omaha, Nebraska utilizing the Simplified Diet method, which included dietary protein counting, as well as free use of fruits and vegetable containing 50 mg/100 grams food or less per serving. After being educated on the use of the Simplified Diet method using a iv written educational tool, participants followed the intervention for an average of 10.5 months. At baseline, phenylalanine levels from the previous year averaged 666 μmol/L; while at follow-up, mean phenylalanine levels significantly decreased to 562 μmol/L (p=0.003). There was no significant difference in mean tyrosine level, body weight, or nutrient intake using the Simplified Diet method. There was a significant increase (p=0.004) in the number of participants who utilized PHE/protein counting compared with only avoiding high protein foods. Several positive attitudes towards the PKU diet were observed after using the Simplified Diet method. Primary themes included “awareness”, “easier” and “realistic.” The results of this study have important implications for clinical management of PKU, as well as individuals living with PKU.