Which type of amino acids must be obtained through the diet?

Essential amino acids are those that the human body cannot synthesize on its own, meaning they must be obtained through the diet. There are nine amino acids classified as essential: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Because the body lacks the necessary pathways to produce these amino acids, it's crucial for an individual to consume them through various food sources, particularly those rich in protein.

In contrast, non-essential amino acids can be synthesized by the body, so they do not need to be provided through diet. Complete amino acids typically refer to proteins that contain all essential amino acids and are often found in animal products. Conditional amino acids are usually non-essential but may become essential under certain conditions, such as stress or illness. Therefore, the focus on essential amino acids highlights their specific dietary requirement for health and proper functioning.