This May Be Why You Feel Sleepy After Drinking Milk
When bedtime comes around, people use many aids to fall asleep: Guided meditation, counting sheep, light reading, sleep supplements, or even a glass of warm milk. In many homes, drinking a glass of warm milk before bed is a time-honored home remedy, meant to calm the body and induce a state of relaxation that leads to sleepiness.
To be clear, the "warm milk before bed" trick doesn't have much scientific backing. However, the reason it has been passed down generations might have something to do with tryptophan. This is one of the human body's essential amino acids. It is often linked closely with turkey because Thanksgiving's favorite bird contains notable levels of tryptophan (about 214 milligrams for a 3-ounce serving), and this chemical compound is often said to make people sleepy. Dairy products like milk contain tryptophan as well — a cup of 2% milk has about 107 milligrams, and a cup of whole milk has about 120 milligrams. Different types of plant-based milk, such as almond and soy varieties, have it too.
A small cog in the machine
When people hear the word tryptophan, sleep is probably the first and perhaps the only word that comes to mind. This is because the body converts this important amino acid into serotonin, which the body also uses to produce melatonin. Both compounds promote sleep and regulate sleep-wake cycles in the human body. While experts are still trying to pinpoint the exact association between milk and better sleep, a glass of it at bedtime may, at the very least, play a small role in the process by introducing tryptophan.
Milk is widely known for being a strong source of calcium and Vitamin D and both of those are also thought to at least play a small part in getting more restful sleep by helping increase the body's production of melatonin — studies linking sleep to both Vitamin D and calcium are ongoing however. Even for those who aren't looking for a sleep aid and just want some milk to pair with your cookies, it could increase serotonin in the brain, leaving snackers more content.