YOU DRANK BOOZE. You ate stuffing. You passed out.
Sound like your Christmas? Sounds like ours, too.
We’re all familiar with the desire to kick off the dress shoes and curl up on the couch after eating two-days’-worth of calories.
But what’s really going on inside your body that brings about that inevitable food coma?
For years, people believed that this sleepy feeling you get after eating – which scientists officially call postprandial somnolence – was due to blood being shunted from the brain to the gut to digest your food.
But studies, such as this one from 2003, have shown that blood flow in the brain and in the gut do not change after a large meal.
The turkey isn’t only to blame, either. The chemical tryptophan, which is present in turkey and does contribute to making you feel sleepy, is actually present in other meats and dairy products in the same, if not higher, concentrations.
The likeliest answer, then, lies not only in how much you eat, but in the number of blood sugar-spiking foods, such as simple carbohydrates, you consume.
While scientists aren’t exactly sure how these types of foods trick the brain into making you sleepy, they can muster a guess.
Carbohydrates are the starches, sugars, and fibres that you get the most of from things like grains, fruits, vegetables, and desserts. They come in two categories, simple and complex, which pass through your body at different rates.
Simple carbohydrates, such as those typically associated with a Christmas meal — white breads, potatoes and refined table sugars — are said to have a high glycemic index because they’re absorbed through your intestines into your bloodstream much more quickly than complex carbs (such as whole grains, brown rice, and quinoa).
When the chewed up food passes into your gut, your body breaks the carbs down into glucose, a type of sugar that provides fuel for your brain and cells. After a heavy meal, levels of glucose in the blood spike upward. Simple carbs cause this spike to happen much more quickly than complex carbs.
This then prompts your pancreas to produce the hormone insulin, which shuttles sugar from the blood into cells for use as fuel, keeping concentrations of glucose in the blood low.
High glycemic meals, with a tonne of simple carbs (cranberry sauce, anyone?), can give you a quick energy boost — but then you crash. They can also actually indirectly increase your levels of tryptophan.
A study from 2007 found that eating a meal with a high glycemic index shortened the time it took for people to fall asleep by about 50% when compared to those fed a low glycemic index meal. The researchers note that the exact mechanism is unknown.
But there’s likely more than one reason a Christmas feast can end in sleepiness. A study from 2009 suggests that cross-talk between the gut and the brain after a meal activates the hypothalamus, which indirectly stimulates regions responsible for sleep while simultaneously suppressing regions responsible for wakefulness.
So there you have it. Go forth. Eat some leftovers. Fall asleep again. You deserve it.
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