Feeling sleepy after Thanksgiving? Don’t blame tryptophan.

It’s a tale told over Thanksgiving tables almost as often as your uncle’s big fish story—eat too much turkey and you’ll be passed out before grandpa switches on the Big Game.

The oft-maligned culprit? Ask anyone and they’ll likely blame turkey, specifically a little molecule called tryptophan.

But does tryptophan deserve its storied reputation? Not quite. Here’s a quick look at what it does—and doesn’t—do.

First off, what is tryptophan?
Tryptophan is an amino acid, a building block for larger molecules called proteins that are responsible for most of the body’s day-to-day functions. It also is a key component for several chemical messengers in the brain, including serotonin and the hormone melatonin, both of which play a role in regulating sleep, among other things.

Humans can produce many of the amino acids we need to survive, but not all of them. Tryptophan is among this group, and must be acquired through our diet.

Now, wait a minute, you might be saying. Chemicals involved in sleep? Acquired through diet? It sounds like tryptophan is to blame for the annual Thanksgiving nap!

Again, not quite.

Turkey isn’t the only source of tryptophan.
Turkey has roughly the same amount of tryptophan as other types of poultry and, in fact, often has less than chicken (270 milligrams for light meat turkey versus 310 milligrams in chicken). Meat, fish, eggs and cheese also contain tryptophan.

It turns out the real reason for your post-feast snoozefest isn’t turkey and tryptophan—rather, it’s likely a result of consuming a whole lot of carbohydrate-heavy foods (mashed potatoes and stuffing, anyone?).

Alright, alright. Tryptophan is off the hook. But what else does it do? Why is it important?
We’re handing this question over to an expert—Dr. Lena Brundin, a physician–scientist in Van Andel Research Institute’s Center for Neurodegenerative Science.

Tryptophan is a critical part of a complex chemical communication network called the kynurenine pathway, which helps regulate inflammation, the body’s response to infection or injury, Brundin explains. If there are issues with the pathway, that can mean trouble down the line.

Normally, inflammation subsides after the problem that caused it is solved—the immune system clearing out a flu virus or your skin healing from a cut, for example—but occasionally, the switches that control it get stuck in the “on” position. The result is chronic inflammation, which has been linked to a host of problems including neurological disorders such as depression and schizophrenia.

“The good news is tryptophan and, really, the entire kynurenine pathway offers a wealth of possible therapeutic targets,” Brundin says. “Finding ways to fix the pathway when something goes awry has massive implications for treatment of these devastating disorders.”

Long story short, tryptophan is important.
Although its claim to fame is largely based on Thanksgiving folklore, you shouldn’t forget about tryptophan. Its sleeping-inducing post-turkey properties may be oversold, but it still is a vital factor in your overall health and wellbeing.

Want to learn more about Brundin’s work? Visit her laboratory website here.