Douglas Laboratories 5-HTP Plus designed for supporting regulation of appetite, mood, and melatonin production. Tryptophan is converted into 5-HTP when it crosses the blood-brain barrier and 5-HTP is then converted into serotonin. Serotonin is a brain neurotransmitter that is key to regulation of appetite, mood and melatonin production. Recommended use: Take 1 capsule daily, or as directed by a healthcare professional.