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

• A. Glycine
• B. Phenylalanine
• C. Methionine
• D. Phenylalanine, Methionine, and Glycine

Answer: (D)

Neonates have rapidly changing and often immature metabolism, so their amino acid needs aren’t the same as adults’. Some amino acids that are essential or commonly required in adults can become risky or harder to handle in newborns if given in higher amounts, so clinicians keep those particular nutrients at lower levels early on.

Phenylalanine and methionine are essential, but their metabolism in newborns is not fully mature. Too much phenylalanine can overwhelm the infant’s ability to process its derivatives, and excess methionine can stress the methylation and sulfur pathways in an immature liver. Glycine, while not strictly essential, participates in many pathways and, if provided in large amounts, can upset the delicate balance of amino acids in neonatal nutrition.

For these reasons, these three—glycine, phenylalanine, and methionine—are typically supplied in smaller amounts to neonates compared with adults, with adjustments as the infant grows and metabolic capacity develops.