Does the Tryptophan in Make you Sleepy?
Myth

Tryptophan in turkey makes you sleepy.

Does the Tryptophan in Turkey Make you Sleepy?

Tryptophan in turkey has a relaxing effect and contributes to sleepiness, but it is overeating and related chemical effects that make you sleepy on Thanksgiving .

What Effect Does Tryptophan Have?

Turkey contains tryptophan humans synthesize tryptophan to make niacin. Niacin helps synthesize serotonin, and serotonin has a relaxing effect. However, being relaxed isn’t the same as being tired, and it isn’t the primary cause of sleepiness on Thanksgiving .

It sounds logical that tryptophan in your Thanksgiving turkey makes you tired, but it isn’t true. Family stress, exhaustion, carbohydrates, and excess in general, which go hand-in-hand with the holiday, (and the related chemical effects) are the root causes of sleepiness. Tryptophan is not the primary culprit here; this is a case of correlation not implying causation.

Although the level of Tryptophan in turkey is quite high, it is actually as high or higher in chicken, milk, eggs, cheese, yogurt, and fish. We don’t expect to fall asleep after a chicken wrap or cheese omelet, so the chemistry must be more complicated that it seems.[1]

Does the tryptophan in turkey make you drowsy? Bytesize Science debunks a Thanksgiving myth.

TIP: Eating turkey can make you sleepy, but tryptophan isn’t the main cause of sleepiness on Thanksgiving (that would likely be your in-laws and excessive eating).

What is the Chemistry of Tryptophan Absorption?

Many protein-rich foods contain tryptophan, an essential amino acid that cannot be manufactured by the body and so must be taken is as food. After a meal containing amino acids, The relatively scarce and bulky acid tryptophan must compete with five other amino acids to cross the blood-brain barrier carried by special transport proteins.
[2]

During a big meal, glucose triggers the beta cells in the pancreas and thereby causes insulin secretion. Insulin is a hormone that transports amino acids and glucose into tissues. Most tryptophan is bound to the protein albumin in the blood, which means it is carried past most tissues into the brain. If it were bound by insulin, like other amino acids, it would have far more competition in crossing the blood/brain barrier.

It is only tryptophan that is already in the system which can be metabolized to produce serotonin and melatonin. Tryptophan is not metabolized during large meals, where it has too much competition in the digestive system. In order for it to be absorbed most effectively into the brain, it should be ingested without any other foods.
[3]

What Makes you Sleepy on Thanksgiving?

If the tryptophan that you consume in turkey is not responsible for making you sleepy after Thanksgiving dinner, then what is? The answer is that a carbohydrate-rich meal increases the absorption of amino acid in the brain leading to serotonin production. Carbohydrates trigger insulin production in the pancreas. Insulin bonds with other amino acids and glucose, leaving tryptophan becomes relatively more concentrated in the blood. Serotonin and melatonin are created, and this is part of what contributes to feeling sleepy.[4]

Fats have a role in the holiday somnolence. Fat takes a lot of energy to digest, especially if you have had your gallbladder removed and lack sufficient bile for the job. Your body will use more than the normal amount of blood in assisting digestion after a big meal than after a small one. The comparative decrease in blood flow will cause a loss of energy elsewhere in your body.

So, in sum, it is a matter of digestion, serotonin, melatonin, and other factors that combine to make a person feel sleepy on Thanksgiving; the tryptophan in turkey is only part of the story.

Does Turkey Really Make You Tired?.

What Else Can you use Tryptophan for?

Tryptophan is available in some countries, although not the United States, to treat mood disorders much the way serotonin is used. Purified tryptophan is being explored in some areas of the world to see if it has a possible link to autoimmune diseases. So far, however, trials are being conducted on mice, not humans.[5]
Japan and South Korea have been using a drug called tranilast developed by Kissei Pharmaceuticals for the treatment of allergies and are exploring other potential uses including possible use in reducing tumors
[6]



Conclusion

There is a lot that happens on Thanksgiving that make people tired, factoring out family and festivities, over-eating in general has a more tiring effect than turkey itself. The exact reasons are chemical and digestion related as detailed on the page.


Citations

  1. The Truth About Tryptophan” Webmd.com
  2. Does Turkey Make You Sleepy?” Scientificamerican.com
  3. Does Turkey Make You Sleepy?” Chemistry.about.com
  4. Does Eating Turkey Make You Sleepy?” chemistry.About.com
  5. Thanksgiving Mystery: Does Turkey Make You Sleepy?” Nationalgeographic.com
  6. Tranilast” nih.gov


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