If you’ve ever had a holiday meal, you’ve probably experienced the repercussions of post-feast fatigue, first hand. While the drowsy feeling is a great excuse to dodge after-dinner-dish duty and park yourself in front of the TV, there is more to it than just the turkey you consumed. The answer might surprise you!
The Truth about Turkey
You might have heard that turkey itself is the reason for your sudden lethargy after a meal, because it contains an amino acid known as L-tryptophan. Tryptophan can be broken down into neurotransmitters called serotonin and melatonin, which are responsible for calming and sleep regulating effects. There’s a catch though: L-tryptophan has to be ingested on an empty stomach, without any other amino acids or proteins, in order for it to have its snooze-inducing effects. The large amount of protein in turkey cancels out the effects of tryptophan. In fact, there may be more tryptophan in other components of your holiday meal than the turkey itself. Pork, spinach and fish all contain as much, if not more, tryptophan than turkey. However, since these foods also contain other amino acids, the effect of tryptophan is cancelled out.
The Proof is in the Pudding
The carbohydrates from your holiday feast are actually more likely to be responsible for your tryptophan-induced, post-feast, drowsiness than the turkey itself. Carbohydrates—the prevailing nutrient in foods like mashed potatoes, pasta, bread and vegetables—stimulate your pancreas to release insulin, which causes other amino acids to enter muscle cells. This results in a higher tryptophan level in the bloodstream, compared to other amino acids, prompting the serotonin release. This is also why carbohydrate-rich lunches often leave you feeling drowsy at your school or work desk, in the afternoon.
Sleepy Sidekicks
There are a variety of other factors that could contribute to a post-dinner nap, as well. The combination of ingesting fats (butter and gravy in particular) and overeating causes your body to redirect blood flow to your digestive system to help break down the meal, which results in less blood flow elsewhere. The decreased blood flow makes you feel tired. Plus, slaving over a hot stove all day can tucker anyone out.
So, turkey alone probably isn’t enough to induce a post-feast hibernation, but the combination of nutrient-rich food in abundance and a festive atmosphere may leave you yearning for a holiday-sized nap.
While you're thinking about taking a nap, you might be interested in discovering Why We Dream or What Would Happen if you Stopped Sleeping?