L-Tryptophan is an essential amino acid - one that must be obtained from food or supplements, as humans cannot synthesize it. L-tryptophan is utilized for protein synthesis, and is metabolized in the body into the neurotransmitters serotonin and melatonin. A small percentage of L-tryptophan is converted into niacin. Clinical studies have shown supplementation with L-tryptophan improves mood and helps sleep. Thorne's pure, pharmaceutical-grade L-tryptophan has undergone numerous quality control tests to ensure its purity and safety. Dosage:1 - 2 capsules tid Each Capsule Contains DV% Tryptophan (as L-Tryptophan) 500 mg * *Daily Value (DV) not established SA501/ 60 A woman who is pregnant or nursing, or who might become pregnant, should consult a health-care practitioner before using this product.