* Science-Based Nutrition * USP Pharmaceutical Grade * Featuring Ajinomoto"s TryptoPure * Dietary Supplement L-tryptophan is an essential amino acid (protein building block) in human nutrition. Essential amino acids are not synthesized by the body and must be obtained in the diet. The L-tryptophan in this product is manufactured and tested for purity according to the Japanese Pharmacopeia (JP) and the United States Pharmacopeia (USP) standards. Vitamin B6 is an essential cofactor in the conversion of tryptophan, while niacinamide plays an important role in allowing our body to properly utilize this essential amino acid.