MadSci Network: Medicine

Re: What causes a hangover?

Date: Fri May 29 15:19:34 1998
Posted By: Robert West, Post-Doc\Functional Neuroanatomist, VA Hospital, Syracuse, NY
Area of science: Medicine
ID: 895331705.Me

Dear Chris

You know, this is something I've wondered about myself. Thanks for giving me a reason to find out the answer.

I'm sure many of us have our own theory on why we get hung over (other than the obvious "I drank too much"). Some of us might say it is dehydration, some might say that its what you drink (red wine and bourbon being nasty, vodka and gin good), some say the trick is not drinking on an empty stomach. The trouble with all of these explanations is that they are stories; they are based on personal experience, or something you heard on the radio, or something you just made up that seems to fit the facts. These ideas may or may not be correct; you just don't know.

Fortunately, over the years some scientists have actually tried to test some of these ideas and see if our perceptions match reality. I've found a few fairly careful experiments that address the causes of a hangover. Not as many as you might expect, given the number of people that miss work and school after a night of partying, but enough that I think I can give you a pretty good idea of what is really going on, and what are just stories we tell each other.

At the outset, I want to say that the only way I can think of to avoid a hangover is not to drink too much. Unfortunately, once you have a hangover, there really isn't anything you can do to make it go away. The only real cure is time.

Essentially, it appears that most of the symptoms of hangover can be attributed to 4 effects of alcohol. First, alcohol upsets your body's water balance. Second, when alcohol is metabolized, it causes your blood to become more acidic than normal (this is called acidosis). Third, alcohol alters the normal daily rhythm of certain body functions. Fourth, alcoholic drinks contain certain impurities called congeners which can be toxic. Together, these 4 effects can turn the day after a party into a nightmare. Typical symptoms of hangover include nausea, ringing of the ears, headache, increased heart rate, excessive thirst, anxiety, insomnia, unsteadiness, dizziness (bed spins), diaphoresis (sweating), shakiness.

What happens the day after

The effects of hangover are triggered by the elimination of alcohol by your body. The physiological and psychological effects of a hangover are strongly correlated with declining blood alcohol levels, and hangover symptoms reach maximum at about the time that blood alcohol levels reach 0.

As anyone who has had a hangover knows, thirst and dry mouth are 2 of the cardinal symptoms. These symptoms caused scientists to investigate how drinking alcohol affects your water regulatory system.

Anyone who has gotten drunk knows that drinking eventually leads to multiple trips to the bathroom. This is because consumption of alcohol causes a decrease in a substance called anti-diuretic hormone (ADH). As blood alcohol levels rise, less ADH is available, and more water is excreted by the kidneys. This situation reverses itself, however, when blood alcohol levels begin to fall, and your body begins to compensate for the temporary, alcohol induced dehydration. ADH levels rise, urinary output decreases, and you become thirsty. By the time the hangover gets into full swing, you are actually retaining fluid, as evidenced by the puffy eyes and face that some people get after a night of drinking. I suspect that this fluid retention, also known as edema, contributes to the hangover headache.

Some of the other effects of hangover appear to be caused by a condition known as metabolic acidosis. Acidosis is when your blood becomes more acidic than it should be. There are a number of reasons why alcohol causes this, but suffice it to say that alcohol interferes with the normal metabolism of some acids, and actually produces others. The end result is a slight increase in the acidity of your blood. This increase reaches its peak during the hangover period, and the level of acidity is strongly correlated with the severity of the hangover symptoms. It takes your kidneys and lungs about 18-24 hours to return the blood acid levels back to normal. It seems likely that the symptoms of nausea and sweating are related to this temporary increase in blood acidity.

The third cause of hangover symptoms is a disruption of some of your normal daily (circadian) rhythms. I have found some studies which observed that alcohol consumption that leads to drunkenness can change the normal daily rhythm of body temperature and brain activity. In those cases, the subjects body clocks were set back about 6 hours; that means that if they woke up at 9:00am after a night of drinking, their body thought it was 3:00am. This could definitely account for hangover grogginess and irritability.

Lastly, some people believe that certain impurities or toxins that can be found in alcoholic drinks, called congeners, can cause hangover. In fact, there is a brand of vodka that used to market itself as so pure that it was hangover free; I believe some governmental agency has since made them stop saying that. In any event, drinks like vodka and gin have fewer congeners, and are supposed to produce less of a hangover, whereas drinks like whisky and red wine, which have lots of non-alcohol ingredients, are supposed to insure a big headache. Along these same lines is the idea that a toxic byproduct of alcohol metabolism (acetaldehyde), builds in the bloodstream and causes hangover.

I suppose I just have a couple of things to say about congeners and acetaldehyde. First, the acetaldehyde hypothesis simply is incorrect; blood levels never really get very high, the levels aren't correlated with hangover symptoms, and it's all gone by the time you actually have the hangover. Regarding the congeners, most of the studies done on hangover used pure alcohol as the drink, so its pretty clear you can get a whopper of a hangover just by drinking alcohol. Second, the scientific studies are all over the map on this point. Some say congeners definitely make a difference, other found no difference whatsoever. It could be that some people are more susceptible than others, or that people get the result they expect to get. Scientifically though, the question hasn't been adequately answered yet in my mind.

Hangover Treatments

Once you have a hangover, there really isn't anything you can do except wait for it to go away. Ibuprofen may help the headache, but the rest just needs time. Of course, one answer would be to avoid the hangover altogether by not overdoing it...

... but most of us at least occasionally do overdo it. And so most of us have our favorite home remedy: a couple of glasses of water and an aspirin before bed; some fruit juice the next morning; another drink (hair of the dog) when you wake up. Or, on the prevention side, not drinking on an empty stomach, not mixing drinks or drinking only "clean" drinks like gin. The question is, is there any scientific reason to believe that any of these really work?

Well, here's what I think about, based on the research I've done.

‘hair of the dog": this works by reintroducing alcohol into your system. Remember, hangover is caused by the elimination of alcohol, so if you put alcohol back in, it relieves the symptoms. The problem is that you are only delaying the inevitable. Unless you plan on staying permanently drunk, you'll have to come down sometime, so this seems a pretty silly, and possibly dangerous, treatment to me.

Eating/fruit juice: Some studies have shown that eating fruit sugars along with the alcohol reduces the subsequent metabolic acidosis a bit, but it didn't affect the severity of the hangover symptoms at all. Fruit sugars taken during the period of hangover didn't help at all, which suggests the remedy of drinking fruit juice the next morning has no real basis. Its probably a good idea to eat before or while you are drinking. It will slow the absorption of alcohol, and it will likely reduce the level of later acidosis, which certainly can't hurt. You should be careful about highly sugary drinks though. The sugar masks the taste of the alcohol, and makes it easier to drink more than you intended.

water and aspirin: It seems like the water is a good idea. Perhaps the best idea would be to drink a glass of water every-so-often throughout the evening. It should reduce the initial dehydration, and therefore likely reduce the rebound edema. It might also keep you from drinking too fast. I would probably choose something like ibuprofen over aspirin, since both aspirin and alcohol can irritate the stomach. I would stay far away from acetaminophen when drinking alcohol; the combination can damage your liver.

mixing drinks: despite popular opinion, there is no evidence that mixing drinks makes you more drunk, or gives you a worse hangover. However, it does appear that some people are sensitive to drinks like whisky or red wine. I suppose I would just drink what I liked, and if it gave a me bad hangover, then stay away from it in the future.

If you have any questions or comments, or would like a list of some of the references I used to construct this answer, please send me an email.

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