A glass of warm milk is known to help you fall asleep. A reputation that seems to be age-old wisdom based on the fact that milk contains tryptophan, one of the essential amino acids that your body uses to make sleep-inducing brain chemicals such as serotonin and melatonin.
But apparently, just consuming a glass of milk won’t make tryptophan to do its “sleep-inducing job.” Why? Because milk also includes other amino acids that decrease the ability of tryptophan to enter the brain.
Carbohydrates trigger a rise in blood sugar levels, which in turn stimulate the release of insulin. Insulin facilitates the entry of tryptophan into the brain, and as a result it can make up for the counteracting effects of other amino acids found in milk.
So, although taking a cookie and milk before bed has been a cliché used for many years, it seems that it isn’t just an old wives’ Tale but it actually holds some scientific fact.