Dietary Supplement. Pharmaceutical Grade Vegetarian L-Tryptophan is an essential amino acid found in mother s milk and many protein foods including turkey, fish, nuts, beans, dairy and eggs. Because it cannot be synthesized by the body, L-Tryptophan must be obtained in the diet. In the body it functions as a precursor to serotonin, the calming neurotransmitter. Healthy levels of serotonin are important for positive mood, restful sleep and balanced appetite. To help assure the purity and potency of every vegetarian capsule Natural Balance uses only pure, pharmaceutical grade L-Tryptophan. Tranquil Tryptophan The stress of living in a fast-paced world with demands of work and family may sometimes leave you feeling tense, anxious, a.