5-Hydroxytryptophan is the direct precursor to serotonin, an important neurotransmitter that participates in the regulation of emotional moods, sleep/wake cycles, pain thresholds, and appetite. 5-HTP was superior to placebo in relieving pain and other symptoms associated with chronic muscle pain syndromes. 5-HTP was superior to placebo in several studies of chronic, recurrent, head pain. 5-HTP has mood-stabilizing properties demonstrated in controlled studies. 5-HTP was superior to placebo for improving the depth and duration of sleep in one study. 5-HTP helped control appetite and improved weight-loss results in three controlled trials. Extracted from plant sources, 5-Hydroxytryptophan is a natural alternative to synthetic L-tryptophan, which is now available by prescription only.