This Is What Really Causes Food Comas, According to a New Study

We've all been there. The spaghetti Carbonara seemed like a great lunch option—as did the accompanying chocolate brownie. But now it's 3 PM and you're in a three-hour accounts meeting. The radiators are on and someone is talking about spreadsheets. You feel your eyelids getting heavier as you sink back into your chair. No one will notice if you rest your eyes for just a minute …

Food comas. We know exactly what causes them and yet we can't stop crawling back into the fuzzy, drowsiness-inducing clutches of carbohydrates and sugar.

But it seems we may have got our favourite sleep phenomena all wrong. The results of a new experiment refute the long-held belief that carbs and sugar cause post-meal energy slumps.

According to neuroscientists at Ohio's Bowling Green State University (BGSU) in Ohio and the Scripps Research Institute, it's not the excessive consumption of these foods that causes postprandial somnolence—the scientific term for a food coma—but protein and salt.

In a recent collaboration involving the two institutes, researchers used fruit flies to explore the neurobiological links between eating, energy levels, and sleep.

BGSU neuroscientist Dr Robert Huber created a computer system that sensed when fruit flies had alighted a small platform and fed from a tube. It measured the quantity and duration of the flies' feed, along with their activity levels and sleep.

As The Independent reports, Huber and his team found that protein and salt caused the flies to become less responsive—in other words, a food coma. They say this is because the bodies of flies—and humans—have to work harder at digesting protein and salt to extract nutrients.

Huber told ScienceDaily: "Clearly, protein is a very expensive commodity. If sleep increases your ability to resorb it, that would be a possible reason. And the same thing with salt."

Despite dietary advice warning that heavy carbohydrates make us sluggish and sugars provide a temporary high before a crash later on, Huber and his colleagues say that these substances did not have the same sleepiness-inducing effects as salt or protein. This could be because carbohydrates are easier to come by in nature, so do not call for such "dedicated digestion," they add.

The scientists have yet to figure out why protein and salt require sleep in order to be digested. In the meantime, you might want to go with soup for lunch if you plan on doing any work this afternoon.