Which set of amino acids is given in smaller amounts to neonates compared with adults?

• A. Phenylalanine and Methionine
• B. Glycine and Tyrosine
• C. Phenylalanine, Methionine, and Glycine
• D. Taurine and Cysteine

Answer: (C)

Neonates have immature metabolic systems and different protein needs than adults, so the amino acid mix used in neonatal nutrition is adjusted to avoid overloading their still-developing pathways. Some amino acids are provided in smaller amounts because—despite being essential or useful—their processing can be less efficient in newborns, and excess can risk toxicity or metabolic imbalance.

Phenylalanine and methionine are essential, but neonates have limited capacity to metabolize and clear these amino acids. Keeping their amounts lower helps prevent accumulation and associated complications as the infant’s liver and related enzymes mature. Glycine, while nonessential, is also kept at a modest level in this context because neonatal requirements aren’t as high as in older individuals, and the goal is to match the infant’s current needs without oversupplying.

Taurine and cysteine, by contrast, are commonly needed in larger amounts for many neonates, especially preterm infants, due to limited synthesis and important roles in development; that’s why this pair would not be described as given in smaller amounts.

So, the combination of phenylalanine, methionine, and glycine being provided in smaller amounts reflects the careful balancing of neonatal metabolic capacity with growth needs.