Ah, the New Year. A time for resolutions, for self-betterment, for dumping out the old and bringing in the new. Unfortunately, if you celebrate New Year’s Eve with champagne and shots, chances are you may spend the first day of the new year on the toilet.
Scientists don’t entirely understand what causes hangovers, but every over-imbiber knows its effects: puffy skin, headaches, nausea, the feeling when you drink water that you just straight-up guzzled acid. And any regular drinker knows the agony and the ecstasy of the hangover poo. It can feel like the only way to relief: the unfortunate, unavoidable end of any excruciating hangover. The morning after the WIRED holiday party—which started with cocktails at a classy bar and devolved, as is tradition, into late-night scream-singing with buckets of beers at a local karaoke joint—saw the shared office bathroom morph into a toxic warzone.
Next-day diarrhea isn’t universal and, for some, alcohol actually causes constipation. But it’s common enough that it has some well-known, and rather unendearing, nicknames—beer shits, day-after-drinking shits (DADS), rum bum, after-grog bog, and so on. Anyone who’s dealt with it knows it can be rough.
But why does it happen?
To start, you have to understand how the body processes alcohol. Food breaks down in the mouth and stomach before nutrients are absorbed into the bloodstream through the small intestine. Alcohol, on the other hand, bypasses some of that system, splashing down into the stomach, which absorbs about 20 percent of alcohol. The rest moves to the small intestine, which absorbs the remaining booze and sends it along to the liver to metabolize. While your liver processes the equivalent of about one drink per hour, the rest of the alcohol circulates throughout your blood system.
Alcohol affects every organ in the human body through the blood stream, including the brain. That’s part of why, when you drink heavily, you stumble around and slur your speech. And particularly relevant to this discussion, alcohol depresses the secretion of anti-diuretic hormone in the posterior pituitary gland. Also known as vasopressin, it helps your kidneys balance the amount of water in your body. Now, because your body can’t hold on to water as it normally would, you start to expel what you don’t absorb—and you find yourself scrolling through Instagram while waiting in the bathroom line to pee. (Once the body catches up, it starts retaining water, which is why you may wake up bloated and puffy.)
Diarrhea is a common side effect of diuretics, sure, but alcohol also inhibits the absorption of liquids in your bowels. Studies of alcoholics show that chronic alcohol consumption affects the sections of the intestine that absorb water and sodium, decreases the activity of the enzymes that break down sugars, and make the mucosa more permeable. All of which leads to—you guessed it—diarrhea.
Plus, when you’ve been pounding boozy beverages—and, hopefully, some water—your body has to process much more liquid than usual. And all the while, the rest of your GI tract is getting wrecked, too. Booze affects the muscles surrounding your stomach and intestine, particularly those that hold on to food for digestion. It also reduces contractions in the rectum, which might “reduce the transit time—and, thus compaction” of the food in your large intestine which, again, can cause diarrhea.
This doesn’t even take into account the indigestion-causing, late-night cheese fries you scarfed down or the mixers you had with your booze. And, depending on the person, artificial sweeteners (see: Diet Coke and rum), gluten (beer), and tannins (red wine) can all cause loose stool.
The best way to avoid a hangover and the dreaded DADS is to eat a balanced meal before imbibing, stay hydrated, and generally take it easy on the booze. But, if you prefer to live on the wild side, be prepared to ride it out the next day in the bathroom. And maybe think about stocking up on Imodium on your way to the party.