Don't blame the turkey. Here's what experts say is really behind your food coma

Do you believe in the holiday food coma?

Many people do. A mainstay on the dinner table at this time of year, turkey contains tryptophan, which is widely believed to be responsible for the uncontrollable yawns and sudden snoozes common after huge family feasts.

"Tryptophan is an essential amino acid needed to make serotonin, a hormone that has many functions in our body, including balancing mood and sleep," said sleep specialist Dr. Raj Dasgupta, an associate professor of clinical medicine at the University of Southern California's Keck School of Medicine.

"The byproduct of the tryptophan-to-serotonin process is melatonin, another hormone that regulates our sleep cycle," he said. "Our bodies do not naturally produce tryptophan, so we have to get it through the foods we eat."

However, many foods besides turkey contain tryptophan, 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 one of the "feel-good" hormones, which can calm and relax the body. However, we don't consume nearly enough turkey during a holiday smorgasbord - even if we go back for seconds - to create the amount of serotonin needed to make us sleepy, said Steven Malin, an associate professor in the department of kinesiology and health at Rutgers University in New Jersey.

To get the amount of tryptophan required to cause a food coma, he said, we'd have to eat about 8 pounds of turkey meat - about half of a typical bird meant to serve a crowd. The US Department of Agriculture recommends planning for 1 pound of turkey meat per person when preparing a holiday meal.