Essential Amino Acids

Eight amino acids are generally regarded as essential for humans: phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, leucine, and lysine.

Cysteine (or sulphur-containing amino acids), tyrosine (or aromatic amino acids), histidine and arginine are additionally required by infants and growing children.

Essential amino acids are so called not because they are more important to life than the others, but because the body does not synthesize them, making it essential to include them in one's diet in order to obtain them.