Another Tryptophan and the Brain Post

Happy Thanksgiving. Let’s talk turkey. Let’s talk tryptophan.

Even though you know all this. You know that for a long time people believed it was the tryptophan in the turkey that made everyone sleepy on Thanksgiving. And then folks pointed out that no, it doesn’t work like that, it’s eating all those carbs, being in a warm house, around loved ones, relaxed, after days or even weeks of the usual sleep-deprived lifestyles we lead.

None of that says what, exactly, tryptophan is, and what it does in the brain. Basically, tryptophan is an amino acid, which are the building blocks of protein. Your body does not make tryptophan itself, and therefore has to get it from foods. You use tryptophan to make Niacin (vitamin B3) which, among other things, is good for your skin.

Tryptophan also makes serotonin, and most of the serotonin in your body is in your intestines, where it regulates movement. The remainder that is in your brain regulates mood, appetite, and sleep. Thus the source of the turkey = drowsiness myth. Serotonin makes you hungry, eating more makes you happy, happiness relaxes you, eating more makes you drowsy, and together the happy/drowsy state puts you to sleep in front of the football game.

From tryptophan to serotonin, and then from serotonin to melatonin. This is the hormone that regulates the circadian rhythm of various parts of your biology. In your brain, this is the cycle that puts you to sleep at the end of the day and wakes you up in the morning—and it’s light dependent, meaning your pineal gland doesn’t make much when it’s light out.

In order to show that turkey makes you actually sleepy, then, it would have to be able to do so in the absence of other things that make you sleepy, and in the presence of other things that keep you awake. We sit down to the table, and eat a ton of food, sending blood to the stomach, which makes us sleepy. We drink wine, which makes us sleepy. We’re sleep deprived already. We’re in a safe, warm, comfortable environment. We’re a little bit bored by the football game between two teams we don’t much care about. It’s cloudy outside, the fall weather, a dark gray sky.

Reverse all that. Eat just turkey, and water, after a good month of 8-hours-per-night of sleep. Keep the thermostat at 65, bicker with your in-laws about why your college team is better than the one’s their children went to, and place a wager on the game: loser does the dishes. Make sure all the lights are on. You will be wide awake, guaranteed.

Nevertheless, your take away from all of this should be satisfaction in the knowing. When one of your in-laws tucks in and hauls out the “turkey makes ya sleep” trope: let them. No need to bicker, no need to argue or educate. Keep your cortisol levels low. Enjoy your non-tryptophan-induced nap. You’ve probably earned it.