Good sleep is probably one of the most essential allies to combat aging. Melatonin is a hormone secreted by the pineal gland that helps regulate your circadian rhythm, the "internal clock" that controls the body's sleep/wake cycle. It also acts as an antioxidant, combating the free-radical damage associated with aging. Melatonin supplements are one of the best choices for people looking to change their sleep schedule. For more information, read our article on melatonin dosage.