Rest Well enhances restful, healing sleep by restoring healthy brain chemistry and produces better brain activity, mood, energy and hormonal balance. L-Tryptophan is an essential amino acid that produces a mood-enhancing neurotransmitter called serotonin. When the body is deficient in tryptophan, it also lacks serotonin. This can inhibit sleep and trigger numerous physical and/or mental disorders. Adequate levels of tryptophan are essential for biochemical balance of the brain.