If, as George Bernard Shaw once said, “whisky is liquid sunshine,” hangovers are a meteor straight to the face. But how exactly does too much of our favorite alcoholic beverage add up to a throbbing headache, dizzying nausea and draining fatigue? Dr. Aaron White, senior scientific advisor at the National Institute of Alcohol Abuse and Alcoholism, helps us break down all the ways booze turns our body against us, culminating in one nasty hangover.
“Alcohol suppresses the release of vasopressin, the hormone that sends signals from the brain to the kidneys telling them to retain fluid,” White explains. This leads us to pee like a racehorse—so much so that if we’re not following each alcoholic drink with a large glass of water, chances are we’ll end up horribly dehydrated. When that happens, the volume of blood in our body drops, since about 60 percent of the human body is water, and blood is one of our largest reservoirs. In order to maintain a steady level of blood pressure now that less blood is flowing through our veins, our blood vessels narrow. Unfortunately, this tightening of the blood vessels also restricts the flow of blood and oxygen to the brain. As a result, the brain tries to compensate by dilating the blood vessels there, leading to swelling and an “I-took-too-many-tequila-shots-last-night” headache.
“Alcohol directly irritates the lining of the stomach and increases acid release,” White explains. Worse yet: Alcohol causes the stomach to drain nearly two times slower than it would otherwise. That means whatever mixture of beer, stomach acid and vodka Red Bull is in there has twice as long to fester into a truly vomit-inducing cocktail.
“While someone might fall asleep faster after drinking, their sleep will be fragmented, and they’ll probably wake up earlier,” White says. That’s because, according to a 1998 study, alcohol reduces rapid eye movement (REM) sleep, decreasing the time spent in the dream state. Unfortunately for us, the dream state is known to be the most restorative part of the sleep cycle, meaning that even if you passed out like a sack of potatoes, you’ll still feel tired and less productive the day after a massive booze session.
Another reason you could be feeling less than alert the morning after is because alcohol is metabolised by the liver into a toxic compound called acetaldehyde. According to a 2007 study by the National Institute of Alcohol Abuse and Alcoholism, “When acetaldehyde is administered to lab animals, it leads to incoordination, memory impairment, and sleepiness.”
Ever feel a little blue after a night of drinking? That’s because of what’s called “glutamine rebound”—in other words, the drinker experiences the opposite symptoms to those produced by the alcohol the night before. “The reduction in anxiety the night before gives rise to heightened anxiety and irritability during the hangover. Sleepiness becomes restlessness. Euphoria becomes dysphoria,” White explains.