Inborn Error of Metabolism—Dietary Advice in Phenylketonuria (PKU) A person diagnosed with phenylketonuria (PKU) is advised to avoid which of the following products due to its phenylalanine content?

Introduction / Context:
Phenylketonuria (PKU) is an inherited deficiency of phenylalanine hydroxylase (or related cofactor pathways), leading to accumulation of phenylalanine and potentially neurotoxic metabolites. Dietary management centers on limiting phenylalanine intake to prevent cognitive impairment and other complications.

Given Data / Assumptions:

• PKU patients require lifelong control of phenylalanine intake.
• Aspartame is a dipeptide methyl ester composed of aspartate and phenylalanine.
• Common foods vary widely in phenylalanine content.

Concept / Approach:
Any source rich in phenylalanine should be restricted. Aspartame, used in many “diet” beverages and sugar-free products, releases phenylalanine upon digestion and therefore must be avoided or carefully monitored in PKU. Carbohydrates like glucose do not directly contribute phenylalanine. Non-essential amino acids (e.g., glycine) and general fats are unrelated to phenylalanine load, though overall diet must still be balanced.

Step-by-Step Solution:

Verification / Alternative check:
Food labels in many countries carry warnings: “Phenylketonurics: contains phenylalanine,” especially on products sweetened with aspartame.

Why Other Options Are Wrong:

• Glycine-containing foods: glycine is not phenylalanine.
• High-fat foods: unrelated to phenylalanine content per se.
• Glucose/fructose: carbohydrates lacking amino acids.

Common Pitfalls:
Overlooking hidden sources of aspartame in beverages, chewing gums, and medications; confusing phenylalanine with other amino acids.

Final Answer:
Aspartame (artificial sweetener)