Tryptophan in the Turkey: A Whodunit (part 2)

See (https://pulsus.wordpress.com/2010/11/27/tryptophan-in-the-turkey-a-whodunit/) for part 1.

The story I crafted in the preceding blog was an exaggeration of the well-known phenomena that occurs across the country after eating Thanksgiving turkey. It was inspired by my nephew, who heard about tryptophan in turkey causing drowsiness. The question of what was responsible for the unconsciousness of the guests around the Thanksgiving table in my story is a little tricky, really.

Turkey does contain high levels of tryptophan, which is an amino acid (a building block of protein) and converts into serotonin. Serotonin is a precursor to melatonin, a hormone that helps regulate our sleep-wake cycle by causing drowsiness. The interesting thing is that the amount of tryptophan in turkey is comparable to the amount in other poultry and meat – equivalent to the amount in chicken, and slightly more than the amount in pork, for example.

The real cause of our drowsiness after Thanksgiving dinner is not all that straightforward. Of course alcohol causes drowsiness, so that must be taken into consideration. But we have to look at what happens when we eat stuffing, mashed potatoes, sweet potatoes, bread, and cranberry sauce. These particular foods (high in carbohydrates) increase our levels of insulin. Insulin helps bring our sugar levels down, but also decreases the amount of certain proteins circulating in the blood by stimulating uptake into muscles. However, tryptophan is not one of those proteins. This leaves a higher percentage of tryptophan circulating in the blood after this type of meal (relative to other proteins). Thus it has a greater advantage in  crossing over into our central nervous system… turning into serotonin….

then melatonin….

you get my drift. (Hopefully not drifting into sleep, though? I will end this shortly).

As far as my multiple choice question from the last blogpost (https://pulsus.wordpress.com/2010/11/27/tryptophan-in-the-turkey-a-whodunit/):

What was the cause of the loss of consciousness of the guests at the Thankgiving table?

A. The wine

B. The mashed potatoes

C. The turkey

D. The maid

E. The butler that was never mentioned

F. The doctor (gasp!)

G. A, B, and C

H. Not enough information to determine

I would have to say “H” is the answer. This is because I have not heard or read of any cases of the tryptophan effect causing a sudden loss of consciousness. As my story was completely fictional, I took the liberty of dramatizing my point.

I hope you had a wonderful Thanksgiving holiday and, if you want to avoid the drowsiness effect next year, I would recommend that you consider eating fewer carbohydrates with your turkey.

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About Linda Pourmassina, MD

Internal Medicine physician.
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