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How A Hangover Works

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"What actually causes hangovers? If alcohol is metabolized after a few hours, why do I still feel crummy the next day?"

-- Alana

If the data is any indication, at least 75 percent of you will recognize this feeling: a throbbing headache, exhaustion, queasiness and even muscle fatigue following a night of overindulging. But what is it about drinking alcohol that causes such discomfort?

The cause is a combination of factors, but primarily one: dehydration.

"Alcohol is a diuretic, so you end up losing water. And the dehydration effect is probably the most severe contributor to hangover," says Dr. Gary Murray, the program director for the Division of Metabolism and Health Effects of the National Institute on Alcohol Abuse and Alcoholism.

The more you drink and the higher the concentration of alcohol in the drinks you choose, the more dehydrated you're going to be. According to an overview of the research, that's because alcohol suppresses the release of the hormone vasopressin, which normally repurposes water released by the kidneys back into the body. With the absence of vasopressin, that water is marked for the bladder and eliminated. Alcohol also causes inflammation of the stomach lining, which can cause diarrhea -- another dehydrating condition.

In the morning, that translates to classic dehydration symptoms: a headache as the body borrows water from the brain, causing temporary tissue shrinkage; thirst; dry mouth; nausea; and even dizziness.

Though dehydration is a major factor, it's not the only one. Everyone has a unique physiological response to alcohol in terms of how it's broken down and eliminated by the body. And the way you metabolize alcohol can certainly have an effect on the onset, severity and duration of a hangover.

Alcohol is metabolized in two stages: one group of enzymes break down ethanol -- the alcohol that you ingest -- into acetaldehyde. Acetaldehyde is a toxic, carcinogenic substance, but soon after a second class of enzymes metabolizes the acetaldehyde into harmless acetate, which is basically vinegar. The problem is that for some people, the second metabolic process can be slower and less effective than in others. That means a build-up of acetaldehyde toxicity, which includes several hangover-like symptoms like rapid pulse, sweating, skin flushing, nausea and vomiting.

Interestingly, there are some ethnic patterns to this variation: Asians, Asian-Americans and Native Americans have a higher instance of a gene that causes inactivity of the enzyme aldehyde dehydrogenase-2 which, along with glutathione, metabolizes acetaldehyde into acetate, according to National Institutes of Health research.

"People with that hypersensitivity to alcohol know it," says Jim Schaefer, a research professor of anthropology at Union College and an expert on alcohol metabolism. "They'll feel a flushing response, they'll feel nauseous after one or two drinks. It's not just during the hangover."

"Whether they choose to ignore that [feeling] has more to do with social factors," he added.

Another contributor to hangovers has to do with the taste of alcohol: congeners. These are byproducts of the distillation and fermentation process that are both good and bad -- while they give alcohol, especially amber alcohols like whiskey and rum, their distinct, full flavor, they're also associated with feeling ill the next day.

"A quadruple distilled vodka is very clean compared to a heavy dark rum and it's probably going to make you feel less sick," says Schaefer.

Let's say you've overdone it. What's the next step? Short of the recommendation to drink in moderation (or not at all), drinking a preemptive glass of water alongside your cocktail or before bed is the best preventive measure, according to all the experts who spoke to Healthy Living. Everyone seems to have their own hangover cure -- either commercial or homegrown -- but what does the research actually show?

"My own personal experience with hangovers -- and I've had a couple -- is that a tall glass of water and an hour of time after I wake up and I'm usually OK," says Murray. "Other people who sell hangover cures or tout things like 'hair of the dog' -- those things are probably less useful. You probably don't need to add a lot beyond water."

Given that dehydration is accompanied by electrolyte imbalance from the loss of sodium and potassium (which might help explain those salty breakfast cravings), rebalancing with a sports drink or alternative might be a good idea. And, for a pounding headache, aspirin or ibuprofen -- rather than acetaminophen, which can cause liver damage, especially in conjunction with alcohol -- can help.

Additionally, Schaefer believes that some commercial treatments that involve activated charcoal have a role in treating and preventing hangovers.

"The charcoal is a very fine compound that filters alcohol compounds -- grabbing them out of the system, shunting them into the lower parts of the small intestine. In a way, activated charcoal acts much like the charcoal slurry given to poison victims in the ER," he says. But other experts are skeptical that the charcoal can effectively target alcohol and its byproducts in a person's system.

It's important to remember that the best way to prevent a hangover is not to drink in the first place -- and to drink moderately if you choose to. If you believe that you or someone you know is abusing alcohol or suffering from alcohol addiction or dependency, there are many resources available such as these provided by the U.S. Centers for Disease Control and Prevention.

Have a question? Ask Healthy Living!

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