What is 5-HTP? 5-HTP is a naturally occurring plant-derived amino acid that participates in the body’s synthesis of serotonin. Serotonin is the chemical messenger that plays a key role in controlling appetite and enhancing mood. The end result: the positive attitude needed to help you maintain a positive, healthy outlook and keep your diet goals. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.