You feel drowsy after Thanksgiving dinner because of the tryptophan in the turkey
November 24, 2011
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No so, but there’s a nugget of truth in the origin of this myth. Tryptophan is an amino acid, and it—or specifically the isomer L-tryptophan—does in fact have the documented effect of inducing sleep. But, you have to take L-tryptophan on an empty stomach, without any other amino acids or proteins, for it to have this effect. I don’t think the terms “empty stomach” and “Thanksgiving dinner” belong in the same sentence! Also, other foods, such as chicken, pork, and cheese, contain as much or more tryptophan than turkey, and you don’t hear people claiming that these foods cause drowsiness.
It’s true, however, that tryptophan may be involved in feeling drowsy after any large, carbohydrate-rich meal. It’s not the tryptophan in the food, however, but the tryptophan that’s already in your body. Eating a lot of carbs causes insulin production, which in turn reduces the blood level of some other amino acids. As a result, the relative concentration of tryptophan in the blood is increased, which leads to more synthesis of the neurotransmitter serotonin, which makes you drowsy. That’s the theory, anyway.
Other reasons for feeling drowsy after Thanksgiving dinner (or most any large meal):
- After a large meal, particularly one rich in carbs and fats, your body directs more blood flow to your digestive system and less to the brain.
- Thanksgiving dinner is often accompanied by a glass or three or eight of wine. Need I say more?
So, snooze to your heart’s content after Thanksgiving dinner, but don’t blame the turkey. Just be sure to wake up in time for sandwiches!