CNN
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Do you believe in the holiday food coma?
Many people do this. A mainstay on the dinner table this time of year, turkey contains tryptophan, which is widely believed to be responsible for the uncontrollable yawns and sudden dozes that follow a family feast.
“Tryptophan is an essential amino acid needed to make serotonin, a hormone that has several functions in our bodies, including balancing mood and sleep,” said sleep expert Dr. Raj Dasgupta, clinical medicine, Keck School of Medicine, University of Southern California Associate Professor.
“A byproduct of the tryptophan to serotonin process is melatonin, another hormone that regulates our sleep cycle,” he said. “Our bodies don’t naturally produce tryptophan, so we have to get it through the foods we eat.”
However, tryptophan is found in many foods besides turkey, including cheese, chicken, egg whites, fish, milk, peanuts, pumpkin seeds, sesame seeds, soybeans and sunflower seeds, according to the National Library of Medicine.
Serotonin is a “feel-good” hormone that calms and relaxes the body. Yet the turkey we eat on our holiday smorgasbord doesn’t produce nearly enough serotonin to make us drowsy, says Steven Marin, an associate professor in the university’s kinesiology and health department. Rutgers University in New Jersey.
To get the amount of tryptophan needed to induce a food coma, we’d have to eat about 8 pounds of turkey — about half the amount of regular turkey served to a crowd, he says. The USDA recommends planning on one pound of turkey per person when preparing a holiday meal.
“It’s unlikely that tryptophan from turkey gets into the brain and produces enough serotonin to make us drowsy,” Marin said.
So you can’t blame sudden drowsiness on a large mouth at a table, says sleep expert Kristen Knutson, an associate professor of neurology and preventive medicine at Northwestern University Feinberg School of Medicine.
“The turkey didn’t really make us sleepy,” Knudsen said. “If we feel sleepy after a big meal, it’s probably because we didn’t get enough sleep in the days leading up to the big event, and we can finally relax after dinner.”
In general, overeating is also a leading cause of feeling tired after eating, Dasgupta said.
“Remember all the delicious side dishes in the middle of a turkey, like sweet potato pie, casseroles, and delicious desserts,” he says. “These savory dishes are high in carbohydrates, which can also lead to post-meal sleepiness.”
Another cause of feeling sleepy after a meal is a change in blood flow from the head to the digestive system.
“Eating a big holiday dinner increases blood flow to the stomach to help digest food, which reduces blood flow to the brain, leaving you tired and ready for bed,” says Dasgupta.
Don’t forget the effects of holiday drinking, either. Many meals served this time of year are finished with wine, cocktails and champagne. Then there’s the omnipresent bear (or two or three) that often accompanies afternoon ball games.
“Honestly, it’s the holidays and there can be some family stress or travel fatigue, so you’re probably drinking more than usual,” Dasgupta said. “Alcohol slows down your brain and relaxes your muscles, so you may feel sleepy after a few drinks.”