Turkey doesn't make you unusually sleepy compared to other meats.

Every Thanksgiving, turkey gets blamed for the post-dinner nap, because it contains tryptophan, an amino acid the body converts into serotonin and then melatonin, both linked to sleepiness. The science behind tryptophan’s effect is real, but turkey doesn’t actually contain an unusual amount of it — chicken, beef, pork, and even cheese contain comparable or higher amounts of tryptophan per serving.

The real cause of holiday drowsiness is much simpler: eating a large, carbohydrate-heavy meal in one sitting redirects blood flow to digestion and can trigger sleepiness on its own, and tryptophan also requires an empty stomach and an absence of competing amino acids to cross into the brain efficiently, conditions a big mixed meal doesn’t provide. Add a glass of wine and an afternoon free of obligations, and the nap has far more to do with the size of the plate than the specific bird on it.