Sleepy after turkey? Bird not to blame

You may have heard that turkey is to blame for your postThanksgiving sleepiness. But although turkey does contain a chemical that makes humans want to curl up in bed, you can’t blame your sluggishness on the bird. Stuffing is the more likely culprit.

Turkey meat contains an amino acid — those are the building blocks of proteins — called tryptophan. It helps the body make important chemicals called hormones, including melatonin. High melatonin levels tell your brain it’s time to go to sleep.

“Melatonin is well-known as being the hormone that lulls everyone to sleep. So people assume that this must be why turkey makes everyone so sleepy,” says Kimberley Chien, a doctor at Weill Cornell Medicine and New York-Presbyterian Hospital whose specialty is kids’ digestive systems. But lots of other foods have tryptophan — even chocolate has it — and some meats contain more of it than turkey does. So why is it just turkey that has a reputation for making us drowsy?

Chien thinks that other Thanksgiving foods give turkey a boost. All of the stuffing, mashed potatoes, rolls and pies you eat are full of sugars, and the chemicals your body uses to digest them happen to make it easier for other chemicals to get to your brain. A sort of wall usually exists between the blood flowing through your body and the blood flowing through your brain, but the process of digesting a tummy full of sugar makes it easier for certain things to slip through. This means tryptophan can trigger sleepytime chemical production more quickly.

Eating a large meal full of fats and sugars will make you tired even without tryptophan, Chien says. When your stomach is full and stretched, your brain gets a signal telling it to send plenty of blood and energy down there to help you digest.