How to Create a PKU-Friendly Diet

Phenylketonuria, or PKU, is a metabolic disorder that causes the amino acid phenylalanine to build up in the blood. This happens because the body is unable to convert phenylalanine into tyrosine, another amino acid. When phenylalanine accumulates in the blood, it becomes toxic to brain tissue.

PKU is an inherited disorder. It’s not contagious and there is no known cure for this condition. However, diet is an important part of managing PKU.

PKU at Birth

Babies born in the United States are screened for PKU shortly after birth. This helps to identify individuals with this condition early so treatment can begin immediately. Early treatment is important to prevent side effects, such as intellectual disability, stunted growth, hyperactivity and seizures. A treatment team typically consists of a metabolic dietitian, physician, geneticist and psychologist. Individuals with PKU are typically monitored from infancy to adulthood.

A strict diet limited in phenylalanine is the main treatment for PKU. Phenylalanine is found in most protein-containing foods such as milk, eggs, cheese, nuts, beans, chicken, beef, pork and fish. While some breast milk can be used, infants with PKU rely on a special metabolic formula that is phenylalanine-free for the first year of their life.

Creating a Unique Meal Plan

As the infant grows and becomes ready for solid foods, a registered dietitian nutritionist with expertise in PKU will create a customized menu for the child. An RDN will work with the child and their family to ensure the diet provides adequate calories, nutrients, vitamins and minerals for optimal growth and development, while focusing on including low-phenylalanine and high-tyrosine foods.

Fruits, vegetables and low-protein grain products are often included in a PKU diet, but because so many foods are off limits with PKU, special formulas are the primary source of calories and essential nutrients.

The PKU-friendly diet needs to be followed for life to maintain serum phenylalanine levels, which are checked regularly. High serum phenylalanine levels can result in lack of concentration, shortened attention span and memory problems. In addition to monitoring blood levels, the metabolic dietitian will regularly review diet records or food journals and growth charts, making adjustments to the eating plan as needed.

Parents of children with PKU need to be creative with foods and should use available PKU cookbooks. Get help with menu planning from a metabolic dietitian and plan ahead for eating out, school lunches, potlucks, trips, vacations and other special events. Try to center special occasions around activities rather than food and encourage your child to be involved in managing their diet as early on as possible.