Does eating turkey really make you sleepy? The truth about tryptophan

The legend of tryptophan in turkey having the power to make people sleepy has become almost as famous as the bird's white and dark meat.

But does Thanksgiving turkey actually induce drowsiness?

"No more so than tuna fish. It's a myth," Dr. Marc Eisenberg, a clinical cardiologist and associate professor of medicine at the Columbia University Medical Center in New York, tells TODAY.com.

"People are sleepy after Thanksgiving because of all the other stuff including the alcohol and just eating too much food."

There are hormones to help with digestion, and when people have a very big meal, those signals can be disrupted, leaving diners feeling lethargic, says Beth Czerwony, a registered dietitian at the Cleveland Clinic's Center for Human Nutrition.

"When you send a ton of food into the digestive system at one time, it just kind of overloads the body so it's not able to regulate the blood sugars and the insulin," Czerwony tells TODAY.com.

"(Blood sugar) might spike and then all of a sudden it drops."

Still, the turkey tryptophan myth persists.

NBC News Health and Nutrition Editor Madelyn Fernstrom suspects it really took off after a 1997 “Seinfeld” episode that featured Jerry and George scheming to make a woman fall asleep so they could play with her antique toy collection.

After they treat her to a big turkey dinner, complete with a box of red wine and lots of heavy gravy, she’s soon snoozing on the couch.

Trytophan is specifically mentioned by the characters as “that stuff in turkey that makes you sleepy.” But that’s not quite accurate.

What is tryptophan?

Trytophan is one of the amino acids, which the body uses to make proteins to help it grow and repair tissue, according to the National Library of Medicine.

The body can’t produce tryptophan, so you must get it from your diet, it notes. Turkey is a good source, but so is cheese, chicken, fish, milk, peanuts, egg whites and soy beans. Tryptophan can also be found in sunflower, pumpkin and sesame seeds.

Amino acids do more than just build muscle — some of them are the “starter” compounds for brain neurotransmitters, Fernstrom says.

“Tryptophan can become serotonin — the brain chemical that calms, causes sleep, among other things — if the right enzymes are around to do so,” she notes.

The body also uses tryptophan to make melatonin, which helps regulate the sleep-wake cycle, according to the National Library of Medicine.

Eating more tryptophan in high-protein foods like turkey does increase the tryptophan going into your bloodstream, but that doesn’t mean your body will turn it into serotonin.

Other amino acids are competing with tryptophan to get into the brain using the same entry “door” and because there are many more of these other compounds than tryptophan, there‘s no impact on serotonin levels with a protein meal like roast turkey, Fernstrom says.

You’d have more success if you were to eat just mashed potatoes or rolls at Thanksgiving dinner: The way to get more tryptophan into the brain and boost serotonin production is by eating pure carbohydrate, she explains. That releases insulin, which lowers the levels of other amino acids, so tryptophan has a chance to get in to the brain without competition.

Why does turkey make you sleepy?

Many people do get very drowsy after consuming a huge Thanksgiving meal. The average dinner can contain 3,000 calories, according to the Calorie Control Council. Don’t blame the turkey for making you sleepy, though.

“That’s due to changes in metabolic activity during digestion. The body has signals to ‘slow down’ and digest the food as a priority,” Fernstrom says.

“And there are changes in glucose and insulin balance that can impact the brain and the digestive system.”

Add the stress of hosting or attending a Thanksgiving dinner, the lack of sleep during the journey to get there, free-flowing alcohol and all the sitting around in front of the TV afterward, and you have the perfect formula for dozing off.

The best solution to stay more alert is to moderate your meal. Try to have a mixed plate of lean proteins, vegetables and some carbohydrates, and watch how much you're eating in general, Czerwony advises.

"Don't try to cram it all in one meal," she says. "We don't want to consume the majority of the calories in one sitting because your body's not going to be able to process it."

That also means having breakfast in the morning so that you're not so overly hungry later in the day that you end up overeating at dinner, Czerwony adds.

Cardiologists suggest making plant-based side dishes as the main dish during the feast instead of eating a huge portion of turkey. They also advise skipping turkey skin, butter and gravy.

And don’t overdo it on the wine. Stick to one or two drinks, or avoid alcohol altogether.

When to eat Thanksgiving dinner for best digestion

Eating the feast between 2 p.m. to 6 p.m. is optimal because it gives the body some time to digest the big meal before you go to bed, says Nancy Mazarin, a registered dietitian in in Great Neck, New York.

"If you're really stuffed, you're not going to sleep well," Mazarin tells TODAY.com. "So if you're going to stuff yourself, the earlier the better."

Czerwony also recommended not eating past 6 p.m., including dessert. Having sweets as close to the dinner as possible will allow them to mix with the protein from the main meal in the stomach, helping prevent the highs and lows in blood sugar when digested, she notes.

People with reflux should take special care to not eat too late.

"Holiday meals tend to be a bit heavier, a bit fattier — that takes longer for our stomachs to digest it. So it's going to be sitting there churning and you may end up getting a bit more of that reflux. That'll make it difficult to go to sleep," Czerwony says.

Many Americans already do this instinctively and prefer to eat the Thanksgiving dinner in the early or late afternoon. About 36% start the feast between noon and 3 p.m., while 38% eat it between 3 p.m. and 6 p.m., according to the Pew Research Center.

This article was originally published on TODAY.com