Supports Relaxation Encourages Positive Mood Promotes Restful Sleep Non-GMO A Dietary Supplement Vegetarian - Vegan Amino Acids Family Owned Since 1968 GMP Quality Assured L-Tryptophan is an essential amino acid; therefore, it is not synthesized by the body and must be obtained from the diet. L-Tryptophan is critical for the production of serotonin and melatonin, which help to support a positive mood, healthy sleep patterns, and proper immune system function. Every lot of NOW L-Tryptophan is tested to be free of Peak E and microbial contamination.