A 2006 study found that popular grape varietals used to make wine, like Merlot, Sangiovese, and Cabernet, contain high levels of melatonin. The study tested the actual fruit, not wine, but the researchers say that melatonin levels in wine may be possible. Don't take this as a good excuse to imbibe before bedtime, however, since alcohol can make it harder for you to stay asleep throughout the night.