Some people believe turkey is the main reason you're sleepy after Thanksgiving dinner. But is it?

The turkey myth - turkey contains tryptophan, an amino acid that forms brain chemicals that make you tired. The fact is Turkey isn't any more sleep inducing than other foods. LiveScience says consuming large amounts of carbohydrates and alcohol may be the real cause of a post-Thanksgiving-meal snooze.

Tryptophan is a component of the brain chemical serotonin, which gets converted into the well-known sleep-inducing hormone melatonin. Poultry and many other foods also contain tryptophan, in similar amounts to that found in turkey. Gram for gram, cheddar cheese actually contains more tryptophan than turkey does... It's the heaps of carbohydrates — the stuffing, potatoes and yams smothered in marshmallows — that are the true problem, according to medical experts. Consuming carbs triggers the release of insulin, which removes most amino acids from the blood, but not tryptophan

Postprandial somnolence (colloquially known as a food coma or carb coma) is a normal state of drowsiness or lassitude following a meal. Postprandial somnolence has two components: a general state of low energy related to activation of the parasympathetic nervous system in response to mass in the gastrointestinal tract, and a specific state of sleepiness. The increased sleepiness is thought to be caused by hormonal and neurochemical changes related to the rate at which glucose enters the bloodstream and its downstream effects on amino acid transport in the central nervous system though there is a lack of evidence to support this. [Wikepidia]

Probably what we are experiencing is the common food coma. Yup, that's it. Look at what Snops.com says:

The truth is, turkey is not to blame for your sleepiness. Chicken and ground beef contain almost the same amount of tryptophan as turkey — about 350 milligrams per 4-ounce serving. While you might have heard someone claim that turkey made them drowsy, you have probably never heard someone say that chicken, ground beef, or any other meat made them sleepy. Swiss cheese and pork actually contain more tryptophan per gram than turkey, and yet the American classic, a ham and cheese sandwich, somehow escapes blame.

The amount of tryptophan in a single 4-ounce serving of turkey (350 milligrams) is also lower than the amount typically used to induce sleep. The recommendations for tryptophan supplements to help you sleep are 500 to 1,000 milligrams.

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