What is the nutrition therapy for phenylketonuria (PKU)?

• A. Ketogenic diet
• B. Provision of a phenylalanine restricted, tyrosine supplemented diet
• C. Increased phenylalanine intake
• D. Normal diet

Answer: (B)

In PKU, the aim is to prevent phenylalanine buildup by tightly controlling intake while making sure tyrosine is available for normal growth and metabolism. Since the body can’t convert phenylalanine effectively, phenylalanine accumulates and can damage the brain, so the diet centers on restricting phenylalanine from natural proteins and using specialized medical foods that provide protein with low phenylalanine content. Tyrosine becomes essential in this condition because it can’t be produced in adequate amounts from phenylalanine, so it is provided through supplementation to meet daily needs. This approach is lifelong and tailored to age and growth, with regular monitoring of phenylalanine levels to adjust the plan. Ketogenic diets, increasing phenylalanine intake, or a normal diet without modification would not prevent the harmful buildup of phenylalanine.