What's in Turkey That Makes You Tired?
For ages, tryptophan (an amino acid in turkey) has been labeled as the sleep-inducing chemical in turkey that makes you tired. But today, we’ll look into why this is likely not the case. Hint: other factors like carbohydrates, fats and alcohol may be the sneaky culprits of your fatigue!
What is Tryptophan?
L-Tryptophan is an essential amino acid, meaning that the body can’t produce it on its own. Instead, we must rely on protein-rich foods like meats, eggs and cheese, which are all natural sources of tryptophan. So why is tryptophan associated with sleep and tiredness?
On Thanksgiving Day, the United States consumes over 46 million turkeys. And what does all of that turkey meat contain? You guessed it, tryptophan, which is how the myth that turkey makes you sleepy was born. Tryptophan helps the body produce serotonin, which is a precursor to melatonin, a sleep-inducing hormone. This reaction can only take place in the brain. It’s important to note this, because once tryptophan enters the bloodstream, it’s pretty difficult for this particular amino acid to get to the brain. Here’s why: 
The Blood-Brain Barrier
Most foods that contain tryptophan also contain other amino acids in much larger quantities, so tryptophan is actually one of the scarcest amino acids. In fact, turkey has only an average amount of the chemical. (Chicken contains much higher amounts of tryptophan.) Once you consume your food, all of the resulting amino acids float around in your bloodstream. In order to get to the brain, they must hitch a ride with special transport proteins to cross the blood-brain barrier. Since the small amount of tryptophan in turkey must compete with all of these other amino acids, the likelihood of getting a free ride is rare. Therefore, the notion that tryptophan makes you tired has its flaws, since so little of it is converted to serotonin from just eating turkey alone. Sure, if one were to consume isolated amounts of tryptophan (with no other amino acids to compete with it) then more of it would be able to convert to serotonin. This is why tryptophan supplements were created during the 1980s as a sleep-aid to treat insomnia. However, it was taken off the market during the 1990s when contaminated supplements caused an outbreak of eosinophilia-myalgia, a deadly muscle-damaging syndrome.
So What Causes Sleepiness at Thanksgiving?
Since tryptophan on its own is likely not the cause of sleepiness, experts say that there are other key factors at play here. Other commonly-consumed foods eaten as part of a Thanksgiving meal are probably to blame, including foods rich with:- Carbohydrates
- Fats
- Alcohol
When carbohydrates enter the bloodstream, they cause the body to produce insulin. Insulin helps the body process these carbs by absorbing them into bodily tissues. Since so many of the foods we eat at Thanksgiving contain carbs, insulin removes the bulk of the amino acids that enter the bloodstream and thereby reduces the competition for tryptophan to get across the blood-brain barrier. As more tryptophan enters the brain, more of it is turned into serotonin. Therefore, can we argue that carbs, not tryptophan, are actually the sleep-inducing agents? Maybe. Experts also say that overeating, a common behavior at Thanksgiving, causes the intestinal lining to stretch. The strain that the gastrointestinal system experiences causes most of the body’s blood supply to be utilized there. The resulting amount of blood being re-routed from the brain can actually cause sleepiness. Furthermore, foods rich with protein and fats are a lot harder to digest, so the body must expend more energy to process these. As for alcohol, there’s no question that it induces drowsiness, even in small amounts. Therefore, the effect of sleepiness is compounded when combined with all of our favorite Thanksgiving foods. 
The Verdict
So does turkey actually make you sleepy? All of our favorite Thanksgiving dishes including pumpkin pie, corn bread stuffing, roasted sweet potatoes and green bean casseroles provide all of the carbs and fats that allow the tryptophan in turkey meat to unleash its sleepy effect on us. Of course, overeating and drinking alcohol doesn’t exactly help you stay awake either. But isn’t that what the holidays are for? After you’ve indulged in the biggest meal of the year, there’s nothing wrong with giving your body what it needs: a well-deserved nap on a memory foam mattress that is designed for ideal comfort.
Updated: 09/13/2019
