5-Hydroxytryptophan, or 5-HTP, is the direct precursor to serotonin, an important neurotransmitter that participates in the regulation of emotional moods, sleep/wake cycles, nerve thresholds, and appetite. Extracted from plant sources (Griffonia simplicifolia), 5-HTP is a natural alternative to synthetic L-tryptophan, which is now available by prescription only. In addition to increasing serotonin levels, 5-HTP causes an increase in levels of endorphins and other neurotransmitters that may be low in some clinical situations. Serotonin is an important initiator of sleep, and 5-HTP has been studied for many positive benefits with sleeplessness. Research also suggests increased serotonin levels may promote early satiety for appetite regulation.