Thanks for the post.... tryptophan is the least abundant essential amino acid in foods. This neurotransmitter takes part in a complicated chain of interactions in the brain that stimulate and regulate our mood and sleep patterns. On the other hand, 5-hydroxytryptophan is a compound derived from tryptophan at a later point in the serotonin formation pathway.Overdosing can produce intense daydreaming and / or wakefulness.