Essential amino acid

Of the 20 amino acids, 9 cannot be made by the body and must be obtained from our diet. These include:

  • The branch chain amino acids (BCAA)
    • Leucine, isoleucine and valine
  • Histidine, lysine, methionine, phenylalanine, threonine and tryptophan

Note that the body can make tyrosine by modifying phenylalanine. Thus, tyrosine is considered a “conditional” amino acid and can be required in the diet when phenylalanine is in limited supply.