What are incomplete proteins?

• A. They lack one or more essential amino acids.
• B. They contain all nine essential amino acids.
• C. They are derived from animal products only.
• D. They are high in fat content.

Answer: (A)

Incomplete proteins are foods that do not provide all of the essential amino acids in sufficient amounts. Essential amino acids must come from the diet because the body can’t synthesize them. A protein is considered incomplete if it is missing one or more of these essential amino acids or supplies them in suboptimal amounts. This is common with many plant-based proteins, which is why eating a variety of protein sources across the day helps ensure you get all nine essential amino acids. In contrast, complete proteins supply all nine essential amino acids in adequate amounts, and they include most animal products and some plant sources like soy and quinoa. The other statements don’t fit because being derived from animal products isn’t required for completeness, and fat content isn’t related to amino acid completeness.