Which of the following statements about essential amino acids is true?

• A. Positive nitrogen balance is when more essential amino acids are consumed than nonessential amino acids.
• B. A protein that contains a high percentage of essential amino acids will be more digestible.
• C. A complete protein contains at least 5 different essential amino acids.
• D. A conditionally essential amino acids is not essential for most of the population but may become essential due to an individual's inability to synthesize it.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the concept of essential amino acids. Essential amino acids are those that the body cannot synthesize on its own and must be obtained through the diet. There are 9 essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
2. Step 2: Clarify the term 'conditionally essential amino acids.' These are amino acids that are typically nonessential (the body can synthesize them) but may become essential under certain conditions, such as illness, stress, or genetic disorders. Examples include arginine, cysteine, and tyrosine.
3. Step 3: Analyze the provided statements. The first statement about positive nitrogen balance is incorrect because nitrogen balance refers to the balance between nitrogen intake and nitrogen excretion, not the ratio of essential to nonessential amino acids. The second statement is also incorrect because digestibility is not determined by the percentage of essential amino acids but rather by the protein's structure and source. The third statement is incorrect because a complete protein contains all 9 essential amino acids, not just 5.
4. Step 4: Evaluate the final statement. The statement 'A conditionally essential amino acid is not essential for most of the population but may become essential due to an individual's inability to synthesize it' is correct. This aligns with the definition of conditionally essential amino acids.
5. Step 5: Conclude that the correct answer is the final statement, as it accurately describes the concept of conditionally essential amino acids in the context of nutrition.