Researchers in Italy think they know why many people like to wind down with a glass of wine at the end of a long day.
Some grapes used to make red wine contain high levels of the sleep hormone, melatonin. This helps to regulate the circadian rhythm, or your daily cycle of activity.
Experts say more research needs to be done to determine whether the red wine compounds are in fact melatonin, or something similar.
The grape varieties that contain the highest levels of melatonin include merlot and cabernet sauvignon.