Complementary Prescriptions L-Tryptophan is a naturally-occurring, essential amino acid that helps boost levels of serotonin, a mood-enhancing neurotransmitter involved in promoting well being, calmness, relaxation, confidence, concentration and appetite control. Taking tryptophan before bed is an excellent way to combat occasional sleeplessness. For best results, take tryptophan on an empty stomach, or with a small serving of carbohydrates. 500mg capsules of pure, pharmaceutical-grade tryptophan in two convenient sizes.