An amino acid naturally existing in foods such as spinach, mushrooms, chicken, turkey, beef, pork, lamb, game, beans, and milk. Considered to be a sedative, tryptophan has been commonly used to treat anxiety, depression, insomnia, migraine headaches, and weight loss. Important as an element for good nutrition, this amino acid is often considered, although falsely, the reason a large turkey dinner makes a person tired and sleepy after eating. It is true it increases the production of serotonin, a natural hormone that works on the body as a calming or sleep inducing agent, but the levels are so small that the effect is very minimal.