How many essential amino acids are there?

10.

There are 10 essential amino acids that humans need in order to survive. These are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, histidine, and tryrosine. These amino acids are essential because they cannot be naturally produced by the body in sufficient amounts, thus they have to be included in the diet.