“I can’t believe I ate the whole thing!” That’s how it starts. How it ends: a nap on the couch, or at least a very unproductive afternoon. In everyday language, it’s known as a food coma, carb coma, or the itis. In scientific terms, it’s called postprandial somnolence (“postprandial” means after a meal, “somnolence” means drowsiness). But why does it happen?
To understand the answer, it’s important to know what happens in your digestive system when you eat. While you’re chewing, your stomach produces the hormone gastrin, which triggers the production of the digestive juices that begin to break down your food. That broken-down food then moves into the small intestine as the gut releases the blood-flow regulating hormone enterogastrone. Meanwhile, your pancreas releases insulin to help your stomach absorb glucose from the carbohydrates in the meal. At the same time, insulin sends a variety of amino acids into the brain, including the infamous sleepy chemical known as tryptophan.
You might notice that food comas don’t happen after every meal — just the indulgent ones. There are a few reasons for this: a meal high in carbohydrates triggers a larger spike in insulin, which makes more tryptophan enter your brain. When that happens, the tryptophan first turns into serotonin, which makes you feel good, and then into melatonin, which makes you feel drowsy. Glucose from the carbs also may block brain cells called orexin neurons, which are responsible for keeping you awake and alert. Read more