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Harvard Commentaries
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Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


Medical Myths Medical Myths
 

The Turkey Coma -- Fact or Fiction?


October 10, 2013

By Robert H. Shmerling M.D.

Beth Israel Deaconess Medical Center


Here's something you may have heard before: Eating turkey can make you sleepy.

The logic behind this idea is that turkey contains lots of tryptophan, a naturally sedating substance. There's just one problem. There's not enough tryptophan in a serving of turkey — or even 10 servings — to have much of an effect. And if it did, you should feel just as tired after a meal of steak or salmon because they contain similar amounts of tryptophan.

It's more likely that you feel sleepy from digesting a big meal. Or, it could be the alcoholic beverages that often go with big meals during the holidays.

Whatever the reason, the "turkey coma" is a medical myth. But let's take a closer look at the tryptophan-turkey connection.

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What Is Tryptophan?

Tryptophan is an amino acid or a building block of protein. It's called an "essential" amino acid because the body cannot make it. Instead, you have to eat foods that contain tryptophan to get enough.

Besides making thousands of proteins, the body uses tryptophan to make serotonin, a key brain transmitter. Serotonin plays a role in the regulation of mood. That's why anti-depressants like fluoxetine (Prozac) target serotonin. Tryptophan also helps induce sleep. So its sedative effects could be related to its role in the synthesis of serotonin.

(Tryptophan is also necessary for making niacin, a B vitamin that is important to skin, nerves and the digestive tract.)

Tryptophan supplements are taken for insomnia in doses that range from 500 milligrams to 3,000 milligrams daily. When used for depression, doses of 8,000 to 12,000 milligrams are common. Meanwhile, a 3-ounce serving of turkey contains about 200 milligrams of tryptophan — about the same as chicken or beef, and significantly less than peanuts or cheddar cheese. In addition, the synthesis of serotonin is tightly regulated so ingesting extra tryptophan will not reliably cause increased serotonin levels in the brain.

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Where Does Tryptophan Come From?

It's not hard to get enough tryptophan. By including the following foods in your diet, adults can easily get the required 200 to 240 milligrams of tryptophan a day:

  • Oats
  • Bananas
  • Tofu
  • Milk, yogurt, cottage cheese, eggs
  • Red meat, poultry, fish
  • Peanuts, sunflower seeds

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What Are the Risks of Too Much Tryptophan?

The risk of ingesting extra tryptophan either through diet or supplements is considered low. Nevertheless, thousands of people became ill in the late 1980s with a newly described condition called Eosinophilic Myalgia Syndrome (EMS) after they took a contaminated supplement. It was sold by a manufacturer in Japan and distributed throughout the world.

As a result, the F.D.A. banned over-the-counter supplements of tryptophan in the United States in 1989. The ban on tryptophan supplements has since been lifted.

Side effects reported with the use of tryptophan include:

  • Dizziness
  • Dryness of the mouth
  • Nausea
  • Loss of appetite
  • Headache

It's unlikely that eating "usual" amounts of turkey would ever cause these side effects because the amount of tryptophan is simply too low.

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The Bottom Line

If you like to eat turkey at Thanksgiving, Christmas or other holidays, you need not avoid it because it might make you sleepy. You're just as likely to feel tired after eating other common foods.

If you really want to remain alert after the big meal, cut down on your portion size, moderate your alcohol intake and take a walk after dinner. By the time you're eating leftovers, you may get tired of turkey — but it's unlikely that turkey will make you tired.

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Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.

 

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