"Turkey makes you sleepy" is a commonly accepted, although false belief that usually crops up most commonly during Thanksgiving and Christmas.
This is one I bought into for many years. I even had a girl tell me that eating some turkey before I go to bed would help cure my insomnia. We hear these "commonly accepted" theories, beliefs, or myths and because most of us are trusting or we hear them from "reliable sources," we swallow them (no pun intended). No real harm is done, just that we absorb a little more false data into our lives and our knowledge. Nowadays, we call it "fake news."
(Image credit: Tony Alter)
Okay, the story is that turkey makes you sleepy because it contains tryptophan. Tryptophan is an amino acid, a protein which is very necessary to human bodies. And true, tryptophan, in certain amounts, can make you sleepy or drowsy. But the fact is that chicken and ground beef each contain almost as much tryptophan as turkey. Cheese and pork actually contain significantly more.
So why does turkey "seem" to make us sleep, especially during the holidays? Possibly because large amounts of it are consumed at holiday meals, along with many other sleep-inducing foods.
First off, the large feasts (i.e. Christmas and Thanksgiving) can induce drowsiness because the large consumption of food slows the body's blood flow.
(Image credit: Stu Spivack)
Other very high-carb foods eaten during the holidays, along with the turkey, definitely aid the drowsiness too. Puddings, pies, cakes, jams, jellies, and biscuits all are high in carbohydrates. Potatoes contain a high amount of starchy carbs. These foods, all customary during the holiday meals, are helpful in sleep inducement.
Particular carbohydrates, tested in experiments with both humans and animals, trigger insulin, which increases the amount of sleep-producing melatonin into the brain. This helps bring about sleep.
Fats, found in large degrees in so many Thanksgiving treats (sweet potatoes with marshmallows, gravy, butter, mince pie, pumpkin pie, whipped cream et al), slow down the digestive system, giving Thanksgiving dinner plenty of time to take effect. Fats also take a lot of energy to digest, so the body will flow blood to your digestive system to tackle the job. Because you have less blood flow elsewhere, you will feel less energetic after eating a meal rich in fats.
(Image credit: Flickr user Mr.TinDC)
Alcohol consumption also may play a part in the traditional after-holiday-meal nap. Wines, ales, "spiked" egg nog and various forms of alcohol are often consumed as a holiday drink or an after-the-meal treat. Alcohol definitely has a relaxing and calming effect on the nervous system, inducing tiredness and sleep.
Another factor is probably the "placebo effect." People hear, over and over, the "fact" of turkey causing sleep, therefore, they convince themselves to get groggy or drowsy and drop off to sleep.
Quite possibly, and probably, if a selected group were inculcated to believe that "hot dogs" or "radishes" or "oatmeal" induce sleep, they would actually fall asleep easier, at least to a certain degree, after consuming these particular foods.
So sleep if you must, but don't blame the turkey!
(Image credit: Flickr user Kris & Fred)