It's long been reasoned that we get tired after a big Thanksgiving dinner is because of the high levels of tryptophan, an amino acid, found in turkey.

Tryptophan is turned into serotonin in our bodies, and serotonin is a chemical thought to aid sleep, among other things. But it's now believed that it's not really the tryptophan in turkey that makes us drowsy after the Turkey Day meal.

For one thing, some scientists say that tryptophan has a greater impact when it is present in an empty stomach (something in rare occurrence at a Thanksgiving meal).

It's now believed that the real reason we become drowsy is because we're often eating a huge meal crammed with carbohydrates: potatoes, sweet potatoes, bread, vegetables, etc. If you're drinking wine with dinner, that'll help make you drowsy too.