What defines a complete protein?

A complete protein is defined as one that contains all nine essential amino acids in sufficient quantities required by the body. Essential amino acids are those that cannot be synthesized by the body and must be obtained through diet. These acids play crucial roles in various bodily functions including muscle repair, immune system support, and hormone regulation.

Complete proteins are typically found in animal products, such as meat, dairy, and eggs, but certain plant sources like quinoa and soy also provide these essential amino acids in adequate amounts. This distinction is important for individuals looking to meet their dietary protein needs, especially in vegetarian or vegan diets where protein completeness can be a concern.

Other options, while related to protein sources, do not accurately define what makes a protein complete. For instance, focusing solely on the source of the protein or its digestibility does not capture the necessary presence of all essential amino acids.