How many amino acids do complete proteins provide?

Complete proteins are those that contain all nine essential amino acids that the human body cannot synthesize on its own. These essential amino acids must be obtained through the diet to support various physiological functions, including muscle repair, hormonal balance, and immune function. Foods classified as complete proteins include animal sources like meat, fish, eggs, and dairy, as well as some plant-based sources like quinoa and soy.

The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Since complete proteins provide all nine of these amino acids, the correct answer reflects the comprehensive nature of these protein sources in fulfilling dietary needs.