Warm milk does seem to help people fall asleep, but the reason for the sleepiness is debatable. Some claim that tryptophan in warm milk is what encourages sleep, according to ZocDoc. Others say that it is a psychological factor that makes warm milk encourage sleep, according to The New York Times.
Drinking a cup of warm milk before bed might bring up memories of a parent helping a child to fall asleep, according to WebMD. Calcium is a nutrient that helps the brain to make melatonin, which is a natural hormone that helps to regulate the schedule of sleep in humans. For the purpose of falling asleep, almond milk might be a good choice.