How many essential amino acids are there?

There are nine essential amino acids that the body cannot synthesize on its own and must be obtained through diet. These amino acids play critical roles in numerous biological processes, including protein synthesis, nutrient transport, and hormone production. The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Understanding the importance of these essential amino acids is key in nutrition as they must be consumed in sufficient quantities for optimal health. Complete proteins, such as those found in animal products, provide all nine amino acids, while some plant sources may lack one or more and need to be combined to ensure a complete amino acid profile.