I’m a huge fan of food so naturally, Thanksgiving is my absolute favorite holiday. We’re only a week away and I can already smell it all in my head: the stuffing, the mac and cheese, and my mom’s famous pecan pie. Of course, I’m also looking forward to the turkey, the mashed potatoes, the gravy, my mom’s green bean casserole, her pumpkin pie, the cranberry sauce…

…where was I again?

Right, so every year at Thanksgiving after we’ve had our fill of these delectable dishes, a certain phenomenon always occurs. That is, everyone starts getting tired.

So why do we get sleepy after our thanksgiving feast?

The most common explanation I’ve heard is that turkey has a lot of tryptophan, which the brain converts into melatonin, the hormone that causes drowsiness. However, this is not entirely true. In fact, turkey has about the same amount of tryptophan as many other meats, about 0.24 grams of tryptophan per 100 grams of food. In comparison, egg whites have about 1 gram of tryptophan per 100 grams of food. So really, high levels of tryptophan in our turkey are not to blame.

Instead of turkey, the real culprits at thanksgiving dinner are the side dishes and desserts. See, dishes like macaroni and cheese, stuffing, potatoes, and dessert all have one thing in common: they contain a lot of carbohydrates. When you eat a lot of carbohydrates, the glucose levels in your blood start to rise, and the body responds to this by pumping insulin into the bloodstream. Insulin tells your body to either use the excess glucose for energy or to store it as fat, because having too much glucose in the bloodstream is toxic. Insulin also stimulates your muscles to soak up a group of amino acids known as BCAA (branched-chain amino acids).

Which brings us back to our dear friend, tryptophan.

While tryptophan is an amino acid, it is not part of the BCAAs. Therefore, as BCAA is continually removed from your blood, the ratio of tryptophan to BCAA increases. This means that when the blood reaches your brain, there is an excess of tryptophan. When that happens, the brain converts the tryptophan into serotonin, and the serotonin into melatonin, the hormone that causes drowsiness.

So to sum everything up, conversion of excess tryptophan into melatonin is the reason you get sleepy after the thanksgiving feast. However, the excess of tryptophan is not a result of your turkey consumption, rather it results from the carbohydrates found abundantly in the side dishes. So this year, let’s be a little more thankful for the turkey.

#dontblametheturkey

Happy Thanksgiving everyone!