Supports Relaxation Encourages Positive Mood Promotes Restful Sleep Non-GMO A Dietary Supplement Vegetarian/Vegan Amino Acids Family Owned Since 1968 GMP Quality Assured NOW Double Strength L-Tryptophan has twice the L-Tryptophan (1000 mg per tablet) as in our regular strength product (500 mg per capsule). 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 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 combination.