There is a naturally occurring amino acid which is the raw material out of which serotonin is made. This amino acid is called tryptophan. Tryptophan is often used to treat poor sleep. It takes about one hour for tryptophan to enter the brain and be converted into serotonin. Some foods which contain elements of tryptophan are eggs, cheese, beans, peanuts and green vegetables.
Milk also contains traces of tryptophan.
That is often why it is suggested we have a nice warm glass of milk before bed or when we cannot sleep. And as the holiday season fast approaches, it may also be good to note that turkey is another source of food which contributes to this sleepiness effect. The sleepiness we experience after eating is called postprandial sleepiness. When planning your holiday feast, remember that it is best not to eat a large heavy meal just before bedtime. Even though it may make you drowsy, consuming a heavy meal will also make your digestive system work harder.