What defines a complete protein?

A complete protein is specifically defined as a protein that contains all nine essential amino acids in sufficient quantities necessary for the body's needs. These essential amino acids are those that the body cannot synthesize on its own and must be obtained through dietary sources.

Complete proteins are commonly found in animal-based foods such as meat, fish, dairy, and eggs. However, certain plant-based sources can also be complete proteins, such as quinoa and soy. Understanding this concept is crucial for nutrition, as it informs diet planning and ensures that individuals receive all necessary amino acids for optimal health and function.

Other options do not accurately describe what a complete protein is. Some may confuse protein completeness with the origin of the protein source or whether it is high in calories, neither of which pertain to whether a protein contains all essential amino acids.