Traditional Versus Simplified Diet for Phenylketonuria: Evaluating the Risks and Rewards

We are excited to announce that we have been invited to submit an application for funding that was developed as a result of the work of the Inborn Errors of Metabolism Collaborative Stakeholder Network. Our proposal is currently under review. For more information on our proposed project, please see the abstract below.

Phenylketonuria (PKU) is an inherited disorder that interferes with the body’s ability to use certain proteins found in foods.  If diagnosed early, and put on a very low-protein diet, individuals with PKU can live a normal life. Before PKU was identified in the 1960s, individuals born with this condition experienced severe intellectual disabilities and were often institutionalized for life. Treatment for PKU consists of a severely restricted low protein diet and the use of specialized metabolic formulas so that “PHE” levels (the offending amino acid phenylalanine) do not build up in the body. Foods that individuals with PKU have to avoid include milk, dairy, meat, fish, chicken, eggs, beans and nuts. Specialized formulas and low-protein foods are available but are very expensive and have not traditionally been covered by insurance. Cost, the extremely limited number of foods allowed, and the burden of calculating PHE in everything eaten, make the “diet for life” very difficult to follow.

Sticking to the strict dietary treatment for PKU is hard, but not sticking to the diet can lead to permanent intellectual disability.   There are currently two key approaches to dietary treatment of PKU, the Traditional Diet or the Simplified Diet.  However, it is not clear which treatment works best for who.

The goal of this study is to determine which of the two treatment approaches, the traditional diet or the simplified diet, produces the best outcomes for individuals with PKU. The outcomes were identified by the IBEMC Stakeholder Network, and include clinical outcomes and quality of life measures.

This study will measure outcomes between individuals with PKU who normally follow traditional diet treatment and individuals who normally follow simplified diet treatment to understand which approach produces the best outcomes. 

The results of this study will allow clinicians to present patients the information needed to make informed decisions about which treatment approach works best for them.

Patient partners will recruit participants from across the nation by referral from the National PKU Association as well as several individual state PKU advocacy organizations.  In addition, 5 metabolic specialty clinics (Wayne State University, Cincinnati Children’s Hospital Medical Center, University of Minnesota Children’s Hospital, Oregon Health Sciences University, and Lurie Children’s Hospital) that follow large cohorts of PKU patients have agreed to promote the study.

This is an observational comparative study consisting of two arms: a prospective arm will compare blood PHE and patient-reported outcomes between individuals with PKU who follow traditional diet treatment and individuals who follow simplified diet treatment; and a retrospective arm will compare participants’ blood PHE level, before and after the switching from traditional diet to simplified diet. 

Outcomes include Quality of Life, Overall Health, Self-Efficacy which will be measured by survey, and PHE levels which are a standard lab test. They will be measured at 0 months, 2 months, 4 months, and 6 months from enrollment. 

Stakeholders participating in this study include clinicians, public health, payers, researchers, and patient partners. Stakeholders will participate in all aspects of the study, including leadership roles on the Advisory Board, as project staff, leading workgroups, and assisting with the dissemination of results.