The real reason you feel so tired after eating turkey

One part of Thanksgiving get-togethers that's just about as traditional as turkey and all the trimmings is a post-prandial nap. It's common knowledge that the turkey itself is to blame for making you conk out in front of the TV while the football game is still on. (Either that, or because it's another blowout and the Lions are losing yet again.)

Turkey does contain high levels l-tryptophan, thought to be a magical, sleep-inducing amino acid. Get enough of that in your belly, and your brain conks out, right? Not so fast, says science, don't blame the turkey. Dawn Jackson Blatner, a licensed dietician and nutritionist and American Dietetic Association spokeswoman, tells WebMD that turkey actually has less tryptophan than chicken, and when is the last time you passed out in the Chick-fil-A drive-thru? (Well, they do have the slowest lines.) Anyway, Blatner says that the real reason why turkey may be making you sleepy is because you ate too much of it, which is another Thanksgiving tradition honored by just about everybody. Blatner points out that "when people overeat food, the digestion process takes a lot of energy," and when you add in the fact that the grown-ups (typically the first to nod off) may have consumed some adult beverages, well, there's your magic sleeping pill, whether you've dined on turkey or tofu.

Another Thanksgiving staple may make you even sleepier

Neuropharmacologist Richard Wurtman of the Massachusetts Institute of Technology's Department of Brain and Cognitive Sciences, tells Scientific American that there's a part of the Thanksgiving meal that does have some serious sleep-inducing properties, but it's not the main dish. Instead, he says that the dessert could be what's making you tired since eating carbohydrates does increase the amount of serotonin in your brain. While serotonin is known as the "feel-good" chemical, part of how it makes you feel good is by helping you get to sleep.

Wurtman explains that carbs themselves don't actually create serotonin, instead, he says, when you finish your meal with a big slice of pumpkin pie, your pancreas starts to make insulin. Insulin, in turn, acts as a kind of a blocker, slowing down some of the amino acids racing to the bran so our old pal tryptophan can get there first. Tryptophan, whether we get it from turkey or any other source of protein, can increase the brain's serotonin levels, but only if carbs have stepped in to keep the competition (other amino acids) away.

So, turkey plus pie plus an overabundance of either or both = zzzzz. Enjoy the nap, though. You're going to need it in order to muster up the strength to work through that mountain of dirty dishes.