Everyday Science: Turkey Day and Tryptophan

We have big plans at our house this Thanksgiving holiday. We are planning on traveling to see family, enjoying our blessings, doing some baking, eating some pumpkin pie, and ingesting some tryptophan.  You’ve heard of this stuff, right?  There are many ways to consume tryptophan, and this coming Thursday mine will have been basted, stuffed, and roasted in the oven for a few hours before being carved and served with cranberry sauce.

I am of course talking about the Thanksgiving turkey, and the natural substance the meat contains, an amino acid called tryptophan.  Actually, it’s an essential amino acid, which means that unlike some other organisms such as plants, humans cannot synthesize it.  Tryptophan can only be gotten as part of our diet.

And if it weren’t for turkey dinners, we would still get tryptophan in our diet— it is naturally occurring in most protein-based foods or dietary proteins.  The wikipedia entry on tryptophan notes that is particularly plentiful in chocolate, oats, dried dates, milk, yogurt, cottage cheese, red meat, eggs, fish, poultry, sesame, chickpeas, sunflower seeds, pumpkin seeds, spirulina, and peanuts. (There is a helpful table with grams of protein in each if you’re interested)

Speaking of interesting, turkey has less tryptophan in it than an equivalent amount of pork chops, egg whites, cod, and caribou.  (I’ve never eaten caribou.  Probably tastes like chicken.  Anyone out there eaten caribou?)  It has only slightly more tryptophan per pound than chicken, beef, or salmon.  So we wind up eating tryptophan all the time, not just at Thanksgiving.

So we ingest tryptophan pretty regularly, it seems.  But what does tryptophan do once eaten?  Why, it synthesizes serotonin!  Serotonin— which is a chemical messenger to the brain called a neurotransmitter—is important— low levels of the neurotransmitter have been found in people with sleep disorders.  So turkey dinner leads to sleepiness, right?

Well, more likely, the vast amount of turkey and trimmings that you plan to consume this Thursday will be the culprit in your post-prandial sleepiness.  That full belly is taking blood supply from the brain in order to digest.  Low blood supply to brain = decreased oxygen to the brain = sleepytime.  Also, wine with your turkey dinner?  All day on your feet cooking?  It’s no wonder you’re sure to be sleepy after that Thanksgiving meal.

I know a good cure to stave off the sleepiness.  Head on over and grab a cup of coffee and another piece of pumpkin pie while you’re up.  I’ll take one too, thanks!


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