5-HTP is a precursor to Serotonin production.* Serotonin is a key neurotransmitter that is manufactured in the brain to help support proper mood, sleep, and appetite functions. Optimal Serotonin levels promote feelings of calm and emotional balance. In addition, Serotonin plays important roles in the bodys ability to respond to pain, and in regulating the appetite by controlling the sensations of fullness and carbohydrate craving.