Melatonin is primarily known as a sleep hormone and a powerful antioxidant. According to a new study, melatonin may even improve the condition of rats that have heart rhythm disturbances with an increased risk of heart attack. Melatonin’s ability to improve the heart function is not related to its antioxidant function, however, and that surprised the scientists behind the study. The new study was presented at an annual meeting for the American Physiological Society (APS) in Orlando. Melatonin has several vital functions, but as we age our endogenous production decreases. Not only does this affect our quality of sleep, it also has a negative impact on the heart and the body’s cells.