Contrary to what you learned while watching Seinfeld, the turkey you're about to eat today is not the true reason why you're bound to crave a nap after dinner. Where the myth stems from: It's true that the amino acid tryptophan is found in turkey, and when it enters the brain, it does eventually convert to melatonin—the sleep-inducing hormone. But as LiveScience explains, it normally has to fight the other amino acids in your body to get to the brain.
Except carbs trigger the release of insulin, which sucks most amino acids from the blood—but leaves tryptophan alone. With a clear course, the amino acid gets through to the brain, leading LiveScience to declare that it's the stuffing and potatoes that are the true culprit. And as far as the tryptophan goes, turkey isn't so unique. In fact, cheddar cheese actually contains more tryptophan than turkey does per gram. For tryptophan to kick in on its own, you'd have to consume it on an empty stomach, the Huffington Post reports.