The Thanksgiving myth goes something like this: turkey contains a large amount of tryptophan, an amino acid that causes drowsiness. So turkey is why we all need our post-Thanksgiving snooze. You’re likely to hear this “turkey makes you sleepy” myth at some point this holiday, probably because there’s a nugget of truth in there: turkey DOES contain tryptophan. But so do lots of protein-rich foods. Turkey has only slightly more tryptophan than chicken, but not as much as soy beans or pork. And it's definitely not the reason you get sleepy after Thanksgiving dinner.
Tryptophan is one of the essential 20 amino acids that humans don’t produce and therefore need to obtain from food. It’s in everything from meat to fish to bananas. As it's ingested, tryptophan becomes a building block for serotonin and melatonin, the compounds in your brain responsible for sleep and mood regulation.
But after you eat turkey, tryptophan’s journey to the brain is slowed by all the other amino acids in your meal. They’re all competing to get into your brain at once, and they end up blocking tryptophan in the process. However, overeating can make you drowsy. So can alcohol. Family stress might also have prevented you from getting enough sleep the night before Thanksgiving. There are plenty of reasons to be drowsy during the holidays. So take a nap, but don’t blame the turkey.