Melatonin is a hormone made by your pineal gland (a small gland inside your brain). Your pineal gland controls your sleep/wake cycle and your body's internal clock—what scientists call your circadian rhythm. Melatonin's main function is to help you fall asleep, but today all sorts of other claims are made for it. Can melatonin cure insomnia, prevent jet lag, block cancer, restore immune function, improve your sex life, and even retard aging? Let's look more closely at what melatonin can really do.
Melatonin does help you sleep. When your eyes notice it's getting dark, that information gets sent to your pineal gland, which then starts to make melatonin, which makes you drowsy. That's why melatonin is sometimes called “the hormone of darkness.” Most people begin making melatonin at sunset, reach a peak at around two in the morning, and then gradually taper off toward sunrise. Until you're about 40, you make plenty of melatonin. After that, you make less and less as you get older, which may be one reason many elderly people don't sleep well.