The Truth About Tryptophan—And the Real Reason It Got a Bad Rap

It happens every year without fail: We balloon our bellies with stuffing, potatoes, and, of course, turkey at Thanksgiving dinner, and as soon as someone starts to nod off at the table, everyone blames it on the tryptophan.

Poor tryptophan. Notorious for being that substance in turkey that makes holiday diners conk out, few people know that it actually plays an important role in the body. More than some cryptic chemical, tryptophan is an essential amino acid that’s necessary for growth in infants and nitrogen balance in adults. The body also relies on it to produce serotonin, the “happiness hormone” that helps regulate mood and gets converted into melatonin (another hormone), which promotes healthy sleep.

So yes, it can make you sleep, but it’s not exactly the lone culprit when it comes to that post–Thanksgiving dinner slump. That myth has pretty much been debunked in the last few years, but what’s the origin story anyway?

Call it a conspiracy theory, but some people have deduced that marketing schemes had something to do with it. Actually, one 1975 study at Tufts University first put tryptophan on the map as a sleep aid, when researchers discovered that in tablet form, it could help insomniacs fall asleep faster and sleep more deeply.

Within a few years—Thanksgiving 1978, to be exact—the Better Sleep Council, formed by the American mattress industry, was touting tryptophan as a way to improve sleep, along with a good mattress of course (wink wink). The Council recommended turkey as a great source of tryptophan—and the notion stuck. Between the initial study, the Council’s report, and tons of subsequent PR surrounding tryptophan, the substance garnered its snooze-inducing reputation. But even though journalists have been trying to put this myth to bed for years, for some reason, the idea continues to have a place at the Thanksgiving dinner table.

Here are the facts. A lot of foods we eat have tryptophan—and often, more tryptophan than turkey. Some examples: spirulina, soy, spinach, crab, soy sauce, shrimp, lobster, pork, watercress, and eggs. But we don’t get drowsy every time we drink a green juice or eat a crab cake or omelette. Okay, maybe we do after brunch—but what else is typically consumed during this Sunday midday meal? Mimosas. (Dun-dun-duuuuun!)

As science has shown in recent years, it’s the entire carb-heavy meal we indulge in—plus the booze—on holidays that really brings on those nap vibes. All the starchy foods in our systems trigger the release of insulin, sweeping out other amino acids save for tryptophan, which becomes free to make its way to the brain to produce serotonin, and ultimately, melatonin. It’s all sweet dreams from there.

So, if you want to be the last man standing after Thanksgiving dinner, by all means, eat that turkey up, if it’s your thing. Just maybe take it easy on the potatoes and gravy. But let’s be real—a good post-dinner nap might not be a tradition we’re quite willing to part with. So bring on those rolls.

Photo credit: Paul Delmont