An essential or indispensable amino acid cannot be made by the body and must be supplied by food. These include isoleucine, leucine, lysine methionine, phenylalanine, threonine, tryptophan and valine. Another amino acid histidine is considered semi-essential because the body does not always require dietary sources of it. Non-essential amino acids are made by the body from the essential amino acids or normal breakdown of proteins. The non-essential amino acids are arginine, alanine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serine and tyrosine.