If you have seen the classic Seinfeld episode where Jerry drugs his date by feeding her Turkey and wine so that he can play with her elusive toy collection, you know just how pervasive the myth of getting sleepy after a turkey meal is. We have all passed out on the couch after a Thanksgiving meal, and many of us have learned to blame the tryptophan found in turkey for our sleepiness. But that is not the whole story.
The truth is, most meats and even shellfish contain tryptophan. Cheese, yogurt, and eggs are also rich sources. Tryptophan is an essential amino acid which the body can’t make, so diet must supply it. The tryptophan converts to serotonin, which then converts to melatonin, which is the amino acid which is sleep-inducing. You may have seen melatonin supplements sold over the counter as a sleep aid.
But if the turkey isn’t the culprit and most of our everyday foods contain tryptophan, why do we get so sleepy after a Thanksgiving meal?
What really makes us sleepy are the substantial amounts of carbs that we typically consume during a Thanksgiving meal. Consuming large amounts of carbs like stuffing, mashed potatoes, yams smothered in marshmallows, and pie triggers the release of insulin. Insulin removes most amino acids from the blood — except for tryptophan. This is how we wind up with more tryptophan in our blood and our brain, which leads to more serotonin, and eventually, more melatonin.
Therefore, while it is true that the amino acid tryptophan really is to blame for your post-meal sleepiness, it’s not really coming from the turkey. It’s the carbs.
Since so many common foods contain tryptophan, is it possible to have too much tryptophan in the body? Not really, says Elizabeth Somer, MA, RD, author of numerous nutrition books. “Except if you end up eating a lot of tryptophan, it means you’re eating a lot of protein and Americans already eat a lot of protein. It’s the only nutrient we get too much of,” she says. “If you’re getting even one serving of 3 ounces of meat, chicken, or fish; a couple of glasses of milk or yogurt; or if you’re eating beans and rice, you will get all the amino acids you need and in there will be the tryptophan,” Somer says.
Another reason you’re so sleepy is overeating. When you pile your plate high with food, digestion takes a lot of energy. That can make you tired. “Studies have indicated that stretching of the small intestine induces sleepiness and a protein–fat loading of the stomach induces sleepiness,” says biologist H. Craig Heller at Stanford University in Palo Alto, Calif., “and, more blood going to the gastrointestinal tract means less going elsewhere,”—for example, the brain or skeletal muscle.
The lesson? If you want to have more energy after dinner this Thanksgiving, eat light and reach for the salad, with maybe just a dollop of potatoes for tradition.