What defines a complete protein?

A complete protein is defined by its ability to provide all nine essential amino acids that the human body cannot synthesize on its own. These essential amino acids must be obtained through the diet, and a protein source is considered complete when it supplies all of them in sufficient quantities.

Complete proteins are crucial for various bodily functions, including tissue repair, muscle growth, and the production of enzymes and hormones. Animal-based proteins, such as meat, dairy, and eggs, are typically complete proteins, while many plant-based proteins may lack one or more essential amino acids, thus categorizing them as incomplete proteins.

In this context, other options are less accurate: a protein containing only plant-based amino acids may not necessarily provide all essential amino acids; a protein lacking essential amino acids cannot be categorized as complete; and a protein synthesized by the body would not be relevant since all essential amino acids must be consumed rather than produced. Understanding the composition of proteins and their dietary sources is important for nutritional science and dietary planning.