The protein known as a complete protein is animal-based proteins such as those found in meat, dairy, and eggs. These proteins contain all essential amino acids necessary for human health, making them critical for various bodily functions, including muscle repair and growth. Some plant-based sources, like quinoa and soy, are also complete proteins, but most plant proteins are considered incomplete because they lack one or more essential amino acids. Consuming a variety of protein sources can help ensure that individuals meet their amino acid needs.