Among the various hormonal supplements that have become popular over the last few years, melatonin has been the first, propelled by the book on the Melatonin Miracle by the Italian researcher Walter Pierpaoli. Melatonin is a hormone secreted by the pineal gland, and among other things, it is largely responsible for regulating wake / sleep cycles. Melatonin supplements will often improve sleep in patients who have a hard time falling asleep or sleeping for a sufficient number of hours. However, melatonin became so popular not because of its effect on sleep but because experiments with laboratory animals have shown that melatonin seems to substantially increase life span.