If you are one of the Americans who eats a portion of the 46 million turkeys eaten in the United States each year on Thanksgiving, you are probably familiar with “turkey coma.”
Whether you only have one or two plates, many can experience an overwhelming drowsy feeling after the Turkey Party Feast that may not seem like any other meal of the year. However, the feeling of fatigue is not just a phenomenon. There’s a reason people want to get to bed after the big feast.
You may have always blamed the traditional main course as responsible for the feeling of fatigue, but turkey isn’t the only suspect behind that feeling of lethargy, says dietitian and nutritionist Nancy Farrell Allen.
“Turkey doesn’t deserve all the credit for those drowsy feelings on Thanksgiving Day,” Allen told USA TODAY.
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What is tryptophan?
While Allen says the turkey doesn’t deserve all the credit for causing the drowsiness, there is actually something in the meat that causes a fatigue reaction.
Turkey contains an amino acid known as tryptophan, which helps the brain release chemicals like serotonin and melatonin. Dr. Donald Hensrud, nutritionist and editor of The Mayo Clinic Diet, told USA TODAY that tryptophan is an “essential” amino acid because the human body does not produce it.
“There are certain amino acids that we need to get through our diet, tryptophan is one of them,” he said.
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Does tryptophan make people drowsy?
The reason tryptophan makes people so drowsy is because of the serotonin and melatonin it produces.
Melatonin is a hormone that regulates a person’s sleep cycle because people can buy over-the-counter dietary supplements to help them fall asleep. Serotonin, commonly known as the hormone associated with happiness, has various functions such as stabilizing sleep, mood, appetite and pain, according to the United States Library of Medicine. The mixture of the two hormones is what Hensrud said is the reasoning for feeling drowsy after eating.
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How many are there in Turkey? Could it really tire you out?
As with all other foods, it all depends on how much turkey you eat on Thanksgiving. If a person ate 6 ounces of turkey, which is double the recommended amount suggested by the University of Illinois Extension Service, there would be 488 milligrams of tryptophan, Allen said.
However, turkey is not the only food that contains tryptophan, and other common foods actually contain higher levels of amino acids than turkey.
Other Thanksgiving foods that contain tryptophan include ham, which, if it eats twice the serving size recommended by the US Department of Agriculture, is equivalent to 507 milligrams of amino acid. Chicken, red meat, and pork also contain tryptophan.
Have you ever been told to drink a glass of milk before bed? That’s because an 8-ounce serving of milk contains 105 milligrams of tryptophan, which Allen said she recommends for patients to help “get peaceful rest at night.” Other dairy products like yogurt and eggs also contain the amino acid.
According to Nutrition Data, turkey ranks 54th of all foods for the amount of tryptophan, behind foods such as eggs, halibut, crab, and lobster.
So why do people feel so tired after Thanksgiving dinner?
Allen and Hensrud say there are many factors that explain why people feel drowsy after a Thanksgiving dinner. While tryptophan can cause drowsiness, Hensrud added that it doesn’t work on its own.
Whether casserole or mashed, potatoes are loaded with carbohydrates, which stimulates insulin production. Hensrud explained that this lowers blood sugar levels, which promotes absorption of amino acids, with the exception of tryptophan. Since it is not being promoted, there is more tryptophan available to influence someone’s fatigue.
Starting the day by not having breakfast or lunch doesn’t help either, as the quick jump in a large amount of food can be overwhelming. After all, the average American eats 3,000 calories during a meal.
“Tryptophan works best on an empty stomach,” Allen said. “And if you haven’t eaten all day, all that food is fasting in no time.”
So no matter what is on the dinner table, the amount of food people eat really affects how they feel.
“If people ate a big meal on Thanksgiving, even if there was no turkey, they would still experience the same type of relaxation / drowsiness after eating,” Hensrud said.