This L-tryptophan supplemment from Viridian is suitable for vegetarians. L-tryptophan is an amino acid, a protein building block that can be found in many plant and animal proteins. L-tryptophan is called an essential amino acid because the body cant make it. It must be acquired from food. L-tryptophan has been indicated in sleep disorders, smoking cessation, attention deficit hyperactivity disorder (ADHD), and anxiety.