What is Tryptophan?

This content was created by the National Sleep Foundation.

You've probably heard the claim that the reason you get sleepy after Thanksgiving dinner is because turkey is high in something called tryptophan. But what, exactly, is tryptophan and does it really make you tired? The connection isn’t quite so direct.

L-tryptophan (the full name) is an amino acid that's found in foods like turkey, chicken, meat, cheese, yogurt, eggs, and fish. Your body uses tryptophan and turns it into a B vitamin called niacin. Niacin plays a key role in creating serotonin, a neurotransmitter that's associated with sleep and melatonin levels (a hormone that controls your sleep-wake cycles). And that’s where the whole “turkey makes you tired” connection comes in.

But it’s not the whole story. You see, eating tryptophan doesn’t immediately impact serotonin levels. Tryptophan is just one of many different amino acids that are contained in foods like turkey. And all of those amino acids compete to get transported to the brain. Tryptophan is one of the least represented amino acids in those foods, which means that it gets shoved out of the way by the others.

That’s where this last piece to the puzzle comes in. There’s one thing that allows tryptophan to easily enter the brain: eating carbohydrates. Carbohydrates cause your body to release insulin, which removes all amino acids—except tryptophan—from your blood. That means that tryptophan has no competition and can enter the brain easily, boosting serotonin levels. So eating a snack that’s all carbohydrates will react with stored tryptophan in your body and give you a much bigger increase of serotonin. You can actually use this to your advantage by eating a light carbohydrate-centric snack before bedtime.

So does a Thanksgiving meal make you feel tired? Yes, but it probably has as much to do with the carb-loaded stuffing that you're eating as it does with the turkey (not to mention the large portions of food, in general!).

Related Reading:

  • How Lions Sleep

    Lions sleep more than most other animals. Learn where, why, and how lions spend so much of the day sleeping.

  • Can You Sleep With Contacts In?

    Since contact lenses reduce moisture in your eyes, in most cases you’ll just wake up with dry eyes if you sleep with contacts in. There are, however, some more serious side effects that can result from overnight contact use. Extended contact use deprives your eyes of oxygen, causing unnecessary strain to the cornea. Wearing contacts lenses too long can potentially damage your cornea’s surface, making your eyes more susceptible to infection. You’re as much as 6 to 8 times more likely to acquire an eye infection when wearing contact lenses while sleeping, whether you fell asleep with them in intentionally or not. Adolescents and young adults are more prone to developing contact lens-related eye infections, which is attributed to less rigorous hygiene.

  • Is it Bad to Go to Bed Without Washing Your Face?

    Bedtime face washing is an important part of your nightly routine. It helps prevent breakouts and creates a relaxing ritual.