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.