Inborn error of metabolism: Individuals with phenylketonuria (PKU) avoid severe neurocognitive impairment if which dietary intervention is implemented early and consistently?

Introduction / Context:PKU is a classic example of how genetics and nutrition intersect. Without treatment, accumulation of phenylalanine and its metabolites damages the developing brain. Early detection and dietary management prevent severe outcomes.

Given Data / Assumptions:

• PKU results from deficient phenylalanine hydroxylase activity.
• Untreated PKU leads to high phenylalanine levels and neurotoxicity.
• Newborn screening enables prompt dietary intervention.

Concept / Approach:The therapeutic goal is to keep blood phenylalanine in a safe range by restricting dietary phenylalanine, found in high-protein foods and aspartame. Tyrosine becomes conditionally essential and is supplemented. Lifelong adherence optimizes cognitive outcomes.

Step-by-Step Solution:Identify toxic substrate: phenylalanine accumulation causes harm.Treatment principle: substrate restriction and product supplementation (tyrosine).Implement low-phenylalanine diet; avoid aspartame; use medical formulas.Thus the correct intervention is phenylalanine restriction.

Verification / Alternative check:Clinical studies show normalized development when dietary Phe is controlled from infancy. Elevated phenylalanine correlates with poorer IQ and executive function.

Why Other Options Are Wrong:

• Tyrosine restriction: counterproductive; tyrosine is often supplemented.
• Homogentisic acid restriction: pertains to alkaptonuria, not PKU.
• None of the above: incorrect because Phe restriction is effective.

Common Pitfalls:Assuming diet can be liberalized in adulthood; evidence supports lifelong management. Hidden Phe sources (sweeteners) can be overlooked.

Final Answer:phenylalanine in the diet is restricted