The holidays are full of rituals and traditions. At my house, Thanksgiving Day wouldn’t be complete without the women doing most of the grunt work while the men eat cheese and crackers, all of us listening to the Chicago Bears game blaring throughout dinner, and my dad hogging all the chocolate pie. Ah, family.
While television sets across the country may be tuned to different football games, I’d bet that one thing we all have in common is the traditional post-Thanksgiving food coma, where everyone slumps over on the couch, too tired to move or wipe the last few crumbs of stuffing off their shirts. Food comas don’t accompany Thanksgiving only, of course; they happen after any oversize meal. There are a lot of myths about what causes this grub hangover—but what’s the truth?
Your Brain on Butterball
Scientists call the food coma postprandial somnolence, which simply means after-dinner drowsiness. If you pay close attention to your body, you’ll notice that a food coma comprises two separate sensations: physically, we feel sleepy and sluggish, and mentally, we feel lethargic and dull.
The parasympathetic nervous system causes our mental malaise. Our parasympathetic and sympathetic systems work together as we eat, but they control opposite processes. When we’re hungry, our sympathetic nervous system (the “fight or flight” system) is active, keeping us alert and on the lookout for food. For an example of this system in action, try going to sleep when you’re famished—it’s darn near impossible. Eating calms down the agitated sympathetic system and simultaneously kicks the parasympathetic system into high gear; the more you eat, the more it gets revved up. The parasympathetic system then produces what’s sometimes called the “rest and digest” response, which controls urination, defecation, and digestion, and commands our bodies to lie down and take a nap.
But that’s just the mental half of a food coma. Postprandial somnolence also causes physical symptoms, which occur because of glucose and insulin. A heavy meal like Thanksgiving dinner is bound to contain foods that rank high on the glycemic index—bread, potatoes, stuffing, and pie—and when we ingest these foods, glucose hits the bloodstream rapidly, triggering the release of insulin. Insulin shuttles glucose into body tissue in an attempt to keep blood sugar constant, and stimulates the absorption of amino acids like leucine, tyrosine, and valine. However, the one amino acid insulin does not affect is tryptophan. As a result, the levels of tryptophan in our blood remain extremely high relative to those of other amino acids, so our brains absorb more of it. All that tryptophan gets synthesized into serotonin, inducing sleepiness.
Most people blame tryptophan itself for our food comas, but that’s not exactly correct. It’s true that tryptophan is a chemical that can induce sleepiness, but turkey does not contain particularly high concentrations of it. The amount of tryptophan in turkey is about equivalent to that of other meats; the foods highest in tryptophan are actually nuts, seeds, bananas, and soy products. Another reason why tryptophan can’t shoulder all the blame is that it works best on an empty stomach, something not likely to be found after a big Thanksgiving meal.
One more myth is that decreased blood flow to the brain is what causes food comas. It may seem logical that after a big meal, blood rushes to our stomachs to aid digestion, diverting it away from our brains—and in some ways, this is true. Some blood is rerouted to our stomachs to help with digestion, but that blood comes only from skeletal muscles. The heart regulates blood flow strictly to the brain and would never let digestion compromise our cerebral capacity.
Wake Up, Sleepy Gut
Some people probably welcome the mellowness in their house when their entire family is conked out, but for those who’d rather be productive for the remaining part of their Thanksgiving Day, there are ways to mitigate the effects of a food coma.
The easiest way to avoid it is also, unfortunately, the most unpleasant: don’t eat so much! Starting the day with a healthy, protein-filled breakfast will keep you fuller throughout the day, reducing the chance that you’ll overindulge. At dinnertime, avoiding the starchiest foods and choosing fresh vegetables is the best way to keep your blood sugar constant and prevent your stomach from getting too full.
Realistically, though, who’s going to pass up seconds of Grandma’s famous stuffing? On this day, even devoted dieters can justify skipping breakfast to save room for second helpings of dessert. One effective way to keep your energy level up after eating is to get moving. Help with the dishes, sweep the floor, stretch, take out the trash … anything to stay active and prevent the coma from setting in. Drink lots of water, which facilitates digestion and keeps the body feeling refreshed. Avoiding alcohol is another surefire way to mitigate postmeal lethargy.
These tips aren’t just for feasting holidays like Thanksgiving or Christmas—food comas can happen after any big meal, and being able to rid your body of sluggishness can be useful after a big lunch at work or school. Any enjoyment of Thanksgiving is probably going to result in some degree of a food coma, but it doesn’t have to paralyze you. Although it may be comfortable to put on a pair of sweatpants and join your family in lounging around in a stuffing-induced stupor, think of how much faster the cleanup process will be if you practice conscious consumption this year.
Updated December 23, 2010