Melatonin is a hormone produced by the pineal gland in the brain, gastrointestinal tract, and retina of the eye. Melatonin release from the pineal gland occurs in response to darkness and is a powerful orchestrator of various body cycles. Besides being one of the most powerful antioxidants yet discovered, melatonin boosts immune function, and plays an important role in sleep. Melatonin levels tend to fall with age. In order to make supplementation of melatonin as safe and effective as possible, we recommend measuring the body's circadian output of the hormone to determine proper potency and timing of dosage. This is done with saliva samples.