Turkey is a good source of L-tryptophan. L-tryptophan is an amino acid, one of about 20 that bind together to make protein. Amino acids and proteins are known as the building blocks of life. L-tryptophan is one of nine amino acids your body cannot produce, so it is known as an essential amino acid -- you must get it through your diet. Your body needs amino acids for a number of reasons, and L-tryptophan, like other amino acids, offer a number of benefits.