The Role of Tryptophan in Autism and Related Disorders

Introduction Tryptophan is an essential amino acid found in many foods. It is abundant in dairy products but meats such as turkey and chicken are a particularly rich source. By the late 1970s it was commonly believed that the primary tryptophan metabolic pathways had been elucidated. The pathway from tryptophan to serotonin (5hydroxytryptamine, 5-HT) and onwards to melatonin had been clarified and the significance of such compounds to depression, mood and the regulation of sleep patterns was reasonably well understood. Serotonin, a product of tryptophan metabolism, was one of the first classes of neurotransmitters to attract the attention of autism researchers as potentially being relevant to the aetiology and pathology of the syndrome. Whilst interest in the role of tryptophan and serotonin to the autistic syndrome continues, the level of research into these important compounds has waned in recent years.