Feeling sleepy after Christmas dinner? It isn't the turkey

If you end up feeling a bit drowsy after Christmas dinner, don’t blame the bird. Turkey does have tryptophan, an amino acid that helps the body make hormones crucial for sleep, “but not enough on its own to knock you out,” says Toronto-based registered dietitian Amanda Natividad-Li.

“The real culprit? All the carb-loaded sides — think stuffing, potatoes, puff pastry and pie — that boost insulin and push tryptophan into your brain, where it’s turned into sleep-promoting serotonin and then melatonin.”

Tryptophan is one of 20 amino acids the body uses to build proteins. Because we can’t produce these amino acids, we need to get them from the food we eat. And while turkey has tryptophan, plenty of other foods have comparable levels — and even higher — without the snoozy connotations.

According to Cleveland Clinic, an 85-gram (roughly three-ounce) serving of turkey has 250 to 300 milligrams of tryptophan, which is similar to the same amount of canned tuna (252 milligrams), red snapper (250 milligrams) and lobster (248 milligrams). You don’t often hear people complaining about needing a nap after a tuna sandwich or lobster roll.

According to McGill University’s Office for Science and Society, when taken as a mood or sleep aid, a typical tryptophan dose is up to four to five grams per day. “A five-kilogram (11-pound) turkey, on the other hand, contains a total of about 12 grams of tryptophan, and one certainly does not eat five kilograms of turkey in one sitting.”

Other animal proteins, including beef and chicken, also have similar amounts of tryptophan. And it’s not just seafood, meat and poultry. Foods such as milk, cheese, yogurt, eggs, oats, nuts, potatoes and chocolate are all sources.

When it comes to tryptophan content, turkey is pretty much in the middle of the pack, Doug Young, an associate professor in William & Mary‘s Department of Chemistry, told a university publication. Many foods contain even more. “Soybeans have about double the amount of turkey. Parmesan cheese. Even pork has more tryptophan than turkey does. There are a lot of foods higher in tryptophan content than turkey — foods we eat more often than we do turkey.”

So, how did the myth that eating turkey makes people sleepy take root? Young credits it to fuzzy science literacy.

“I think that it’s just one of those urban myths that developed because people misunderstood the science. And tryptophan does lead to the production of serotonin and melatonin, which may lead to this kind of drowsiness, so people misappropriated it, and they didn’t really think about the true biochemical mechanisms behind the whole thing.”

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