Somehow, someway, the idea that a chemical in turkey — tryptophan — causes the after-Thanksgiving Day meal sleepiness has crept into public consciousness.

“You can’t stop it,” said Scott Beyer, professor of animal sciences at Kansas State University, of the perpetuation of the popular myth. Beyer answered a few questions about the issue to try to clear up the misconceptions.

What is tryptophan?

An essential amino acid found in a wide variety of foods, tryptophan plays a small role in regulating sleep, Beyer said, but the amount in turkey is minimal. In addition, Beyer said the body self regulates absorption of tryptophan, so even if you ate a large amount of foods containing it, your body would adjust, minimizing tryptophan’s effects. Tryptophan also can be found in eggs, cheese, fish, nuts and soy products, among others.

So what causes the sleepiness associated with the Thanksgiving Day meal?

“There’s so many things you can point to,” Beyer said. The biggest factor in the post-meal sleepiness is most likely the high amount of calories many people consume during the meal, which often includes foods high in carbohydrates. “The volume, that’s huge,” Beyer said. Add in snacking on desserts following the meal, and “you’re done,” he said.

What’s the best way to avoid the post-meal slumber?

With all the options typically available during a Thanksgiving Day meal, people still “can eat a good, healthy meal,” Beyer said. But cutting down on the volume, as well as desserts and carbohydrates in particular, can help. Beyer also said that a little exercise, such as a quick walk, can help keep Thanksgiving Day meal-munchers awake.