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It’s Not the Turkey That Makes You Tired
What’s really behind the sleepiness after a hearty Thanksgiving meal
If you’ve ever had an unstoppable urge to crash on the couch after eating — the most common example is after a hearty Thanksgiving dinner — then you’ve experienced what scientists call “postprandial somnolence,” or in layperson’s terms, a food coma.
There are a number of popular theories about what causes people to feel tired and sluggish after eating, including the Thanksgiving turkey. Turkey (and a number of other foods, like chicken, fish, cheese, yogurt, and eggs) contains an amino acid called tryptophan, which is the alleged culprit behind your tiredness. But experts say suggesting the tryptophan in turkey contributes to food-coma feelings is a bit of a leap, and reads like such: In your body, tryptophan is converted to niacin, a B-vitamin that helps the body create serotonin, which is a mood-boosting hormone, that can help regulate sleep.
According to David Levitsky, PhD, professor of nutritional sciences at Cornell University, it’s true that turkey contains tryptophan, and that tryptophan is a precursor to serotonin. But there’s no scientific basis to the assumption that eating turkey would cause someone to feel tired, primarily because there’s not enough tryptophan in turkey to impact the brain.
“There’s a whole area out there called fantasy nutrition, where people take a little knowledge and blow it out of proportion,” he says. “The amount of tryptophan we’re talking about in turkey is so trivial compared to what is necessary to alter brain serotonin, that it doesn’t really make any difference,” he says.
Levitsky says the sheer amount of food we eat on occasions like Thanksgiving is more likely to trigger a food coma — and it has to do with the autonomic nervous system, the same system involved in the fight-or-flight and rest-and-digest responses.
The stomach and intestines contain stretch receptors, neurons that detect digestion and send messages to the brain about our physiological state. The act of eating puts the autonomic nervous system into parasympathetic mode (also known as the rest-and-digest response) so the body can conserve energy for digestion.
