What term describes amino acids that are normally nonessential but become essential under certain conditions?

• A. Conditionally essential
• B. Nonessential
• C. Essential
• D. Conditionally inessential

Answer: (A)

Conditional essentiality of amino acids.

Some amino acids are normally produced by the body in sufficient amounts, so they’re considered nonessential. Others must come from the diet because the body cannot synthesize them in adequate amounts under certain circumstances. These are normally nonessential but become essential when conditions such as illness, severe stress, or developmental needs increase demand or impair synthesis. That’s why certain amino acids—like arginine in infants or tyrosine when phenylalanine metabolism is impaired—are labeled conditionally essential.

The term “conditionally essential” captures this situation. Nonessential would imply they’re always synthesized adequately, essential would imply they’re always required from the diet, and “conditionally inessential” isn’t a standard term used in nutrition science.