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My Chemical Reaction: Tiredness and Turkey

Published on 20 November 2017

From your mother’s dry turkey to Grandma Joann cheating at checkers, Thanksgiving traditions die hard. Perhaps one of the longest-standing Thanksgiving traditions is the annual dinner discussion about how turkey makes us tired.

The origins of this pesky factoid are uncertain, but Jeramia Ory, Ph.D., associate professor of biochemistry, took some time to explain the science of tryptophan and its connection to our annual Thanksgiving nap.

What is tryptophan?

Tryptophan is one of the 20 amino acids that make up a protein. It is an essential amino acid, meaning we have to get it from our diet, as our body does not produce it on its own.

What about tryptophan makes people tired?

Tryptophan doesn’t necessarily make you tired. However, when we consume protein, our body breaks it down into individual components. After we eat a high-protein meal, the protein gets broken down into amino acids that are transported through the blood stream. If the tryptophan makes its way to the brain, it can be converted through a series of reactions—from tryptophan to an intermediate and then to serotonin. The serotonin stored in the nerve cells then signals to the other nerve cells. If need be, the serotonin can be further broken down into melatonin, a hormone well known to regulate sleep. But at the top of that chain is tryptophan. If you don’t consume tryptophan you won’t produce any serotonin and therefore no melatonin.

That being said, consuming large quantities of tryptophan doesn’t make you immediately sleepy. It is a slower process that does more to regulate sleep.

Where does turkey measure up on the levels of tryptophan compared to other proteins?

Though turkey has high levels of tryptophan, it is not the protein with the highest. Red meats and chicken actually have higher levels of tryptophan than turkey.

If the tryptophan in turkey is not the reason for sleepiness, what is?

There is a study that looked at caloric intake and sleep. After consuming a number of calories, the subjects of the study would take a nap. The study measured the subjects’ ability to fall asleep and how long it took. As the calories consumed increased, the subjects fell asleep faster—regardless of whether it was carb heavy or a high-fat meal.

People tend to consume far more calories during Thanksgiving than they do during typical meals. Compound that with the hectic activity of the holidays, and it makes sense that we get sleepy..

Any advice to curb the sleepiness?

The boring advice is to eat less—and maybe drink a lot of coffee.

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