(Rachel Orr/The Washington Post; iStock)

Dear Science: How do I prevent my horrible hangovers? Isn't there any way to make it stop?

Here's what science has to say:

Oh, boy. Do we have a cure for you! There is a fool-proof, sure-fire, scientifically proven 100 percent effective way of stopping a hangover from happening, and it can be yours free:

Don't drink.

(If you need a moment to roll your eyes, go ahead. It's fine. We'll wait.)

If you're going to drink — and it's cool if you do! We're all adults here — do so slowly and in moderation.

At least part of hangover stems from the way alcohol is metabolized. Enzymes in your liver break down ethanol, the ingredient that makes alcohol so intoxicating, into a compound called acetaldehyde. It's highly toxic — the International Agency for Research on Cancer says it should be classified a carcinogen — and triggers an unpleasant inflammatory response. A 2000 study found that elevated acetaldehyde levels lead to increased skin temperature, facial flushing, elevated heart rate, lower blood pressure, dry mouth, nausea and headache. (Long term, it's also a cause of liver cirrhosis.)

Acetaldehyde only lives in your gut for a very brief period, but if you drink too fast, the enzymes responsible for breaking it down into the more benign chemical acetate won't be able to keep up. So the advice you got from your college health counselor freshman year — pace yourself, alternate alcohol with water — is actually pretty good.

But acetaldehyde is not the only thing making you feel miserable after a night of too much celebrating. There are a host of other factors at work, and scientists still are not really sure which of them contributes to alcohol's awful after-effects.

Here's a scientific explanation of what causes hangovers and how you can prevent them (other than, you know, drinking responsibly). (American Chemical Society)

"The challenge is it’s a lot more complicated than anybody wants it to be," said John McGeary, a clinical psychologist at Brown University and member of the international Alcohol Hangover Research Group. (Yes, that is a real thing, and no, its membership is not composed of frat guys.)

"There’s not really great consistent evidence [for any one cause] and that's probably due to the fact that it’s such a complicated problem that's caused by many small effects that all together make you miserable," he added. "There’s a tremendous difficulty in pinning down any one source ... so the bottom line is we still don't exactly know what causes a hangover."

The nasty effects of acetaldehyde can be exacerbated by congeners, the chemical extras that result from fermentation. These compounds are part of what make each alcohol distinctive, but they can also make their hangovers more potent. Studies suggest that dark alcohols, which have more congeners, contribute to worse hangovers than light ones; mixing alcohols — thereby mixing congeners — may make that effect even worse.

Ethanol, alcohol's active ingredient, also messes with your body in various ways. It suppresses the hormone that helps your body retain water, meaning that for every ounce of alcohol you consume, you'll have to pee eight times that amount. That will leave you dehydrated, which hardly helps your morning after nausea and headache, so it is a good idea to drink water during and after drinking.

On the slightly ickier side, ethanol "speeds up passage in the GI tract," as McGeary politely put it, explaining why a night of heavy drinking may have you running to the bathroom. It also irritates the cells in your stomach lining, making you want to vomit.

These factors will contribute to your hangover, but whether or not you get one isn't always up to you. How your body handles alcohol is largely a product of genetics. Some lucky people — roughly a quarter of the population, according to a 2008 literature review — do not get hangovers at all. Other groups, particularly people from East Asia, have a genetic variant that makes it harder for them to metabolize acetaldehyde, so their hangovers are much worse.

Even if your genes allow you to drink your friends under the table, it's possible for your body to lose its ability to metabolize alcohol. The mushroom Coprinopsis atramentariamore commonly known as the inky cap or "tippler's bane," contains a compound called coprine that keeps your body from breaking down acetaldehyde. If you consume alcohol and these (otherwise harmless, and even delicious) mushrooms within a few hours of one another, you're in for a world of hurt. Vomiting is usually the worst of it, but if you truly tipple in excess after eating an inky cap stir fry, you run the risk of cardiac arrest.

Scientists have been working to exploit these chemical reactions and genetic quirks to treat another alcohol-related problem: addiction. One medication approved for alcohol dependence disrupts the body's ability to metabolize acetaldehyde.

"It's very uncomfortable and you get very sick frequently," McGeary said. "They wake up and vomit and report they don’t ever want to drink again — at least, not on the medication."

These kinds of medications highlight one reason why it's important to study hangovers, McGeary said.

"To be honest I think the field of hangover research has been somewhat marginalized and even trivialized," he said.

There's a tendency to view drinking as a vice, and hangovers as our rightful punishment. But hangovers cost an estimated $224 billion in lost productivity each year in the United States alone, according to the Centers for Disease Control and Prevention. And McGeary thinks that understanding what causes hangovers can help researchers better understand why people drink — and how to help them when they drink to excess.

One thing that is clear is that once you have a hangover, nothing but time can cure it — no matter what your older sister or a late night infomercial tell you.

A review of research in the British Medical Journal tested dozens of purported "remedies" for hangovers — including cabbage, coffee, eggs, and a disgusting concoction involving olive oil, raw egg yolk, tomato ketchup, Tabasco sauce, Worcestershire sauce, lemon juice and buttermilk — and found "no compelling evidence exists to suggest that any conventional or complementary intervention is effective for preventing or treating alcohol hangover." The scientists especially don't recommend "hair of the dog" — drinking more alcohol in the morning. At best, it just dulls your senses for a while, delaying the inevitable. And it can make your misery only worse.

There's not much you can do aside from drink water, take a pain reliever (but not acetaminophen, because your poor liver needs a break) and ride it out. Your body will thank you. And then quietly ask if next time, possibly, you'll consider drinking a little less.

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