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Somewhere between giving thanks and reaching for that second slice of grandma’s pumpkin pie, it hits—the “food coma.” While it’s common to feel tired after a big meal (especially a holiday feast), research shows it’s more than the tryptophan-filled Thanksgiving turkeys that can lead to a post-dinner snoozefest.

Don’t Blame the Bird—Why It Matters

The truth is, turkey doesn’t even contain that high a concentration of tryptophan, the sleep-inducing amino acid, compared to other types of poultry, pork, and even cheese. So what’s the science behind postprandial somnolence, the fancy name for the sleepy, sluggish feeling that strikes after eating a big meal? Debunking a myth: Neurohormonal and vagal modulation of sleep centers, not redistribution of blood flow, may account for postprandial somnolence. Bazar, K.A, Yun, A.J., and Lee, P.Y. Department of Dermatology, San Mateo Medical Center, San Mateo, CA. Medical Hypotheses, 2004; 63 (5): 778-82.

For starters, holiday menus don’t tend to shy away from high-calorie and high-fat dishes. And when second (or third) helpings of those heavy-hitters go down, blood flows to the digestive system to ramp up its efforts. As a result, the rest of the body’s systems (including the brain) can start to feel a slowdown. Think of this as “rest and digest”— the opposite of the “fight or flight” response. Debunking a myth: Neurohormonal and vagal modulation of sleep centers, not redistribution of blood flow, may account for postprandial somnolence. Bazar, K.A, Yun, A.J., and Lee, P.Y. Department of Dermatology, San Mateo Medical Center, San Mateo, CA. Medical Hypotheses, 2004; 63 (5): 778-82.

Another reason we feel the sudden need for zzz’s is thanks to high glucose levels in the blood stream. This triggers the release of insulin, which absorbs all amino acids—except for tryptophan. High-glycaemic index and -glycaemic load meals increase the availability of tryptophan in healthy volunteers. Herrara, C.P., Smith, K., Atkinson, F., et. al. University of Sydney, Sydney, NSW, Australia. The British Journal of Nutrition, 2011 Jun; 105 (11): 1601-6. Effects of tryptophan loading on human cognition, mood, and sleep. Silber, B.Y. and Schmitt, J.A. Cognitive Sciences Group, Lausanne, Switzerland. Neuroscience and Biobehavioral Reviews, 2010 Mar; 34 (3): 387-407. Hello, heavy eyelids! Research also shows spikes in glucose can effectively switch off the neurons in the brain responsible for keeping us up and at ‘em. Glucose overload can also switch on the neurons that promote sleep (and turn us into those lazy couch potatoes). Glucose-sensing neurons of the hypothalamus. Burdakov, D., Luckman, S.M., and Verkhratsky, A. The University of Manchester, Manchester, UK. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 2005 Dec 29; 360 (1464): 2227-35.

Think Before You Eat (a Lot)—The Answer/Debate

Why You're So Tired After a Big Meal

A post-meal nap might feel as much a tradition as watching the Macy’s Thanksgiving Day Parade, but here are some tips to avoid sleeping the whole day away:

  • Start smart. To avoid overeating later on, try starting the day with a protein-rich breakfast, and consider breaking up that one massive meal into two smaller meals spaced a few hours apart.
  • Lighten the carb load. It’s recommended to eat between 225 and 325 grams of carbohydrates daily, but take it easy on the starchy side dishes. Sorry, mashed potatoes and cornbread, that means you.
  • Lay off the booze. Alcohol can slow down digestion, so consider raising a glass of water for that holiday toast instead.
  • Get moving! Play a backyard flag football game, go for a walk around the neighborhood, or (at the very least) offer to do the dishes to get that digestion, well, moving along too!

Originally posted November 2011. Updated November 2015.

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