What Causes a Hangover

hangoverToday I found out what causes a hangover.

There are several things that contribute to hangovers, but one of the principal factors is simple dehydration.  Alcohol has a dehydrating effect by inhibiting the release of vasopressin, which is an anti-diuretic hormone.  So, in layman’s terms,  the result of alcohol inhibiting the vasopressin is that your body produces a lot more urine than normal, with the result that you become dehydrated easily. This dehydration is a major contributor to the headache, dry mouth, and general feeling of lethargy that is often experienced during a hangover.

Another major contributor to a hangover (many think even more significant than dehydration) is acetaldehyde.  Acetaldehyde is produced when alcohol is converted within your body by the enzyme alcohol dehydrogenase to acetaldehyde.  Why’s this bad?  Acetaldehyde is a carcinogen in humans and has been shown to cause damage to DNA, as well as abnormal muscle development when it binds to proteins, among other negative side effects.

Acetaldehyde eventually gets converted to the much more safe (for your body) acetic acid.  However, some people’s bodies contain a genetic deficiency where their bodies don’t convert acetaldehyde to acetic acid very well or at all.  These people have been shown to be significantly more prone to severe hangovers.  They are also ultimately more prone to Alzheimer’s disease, various organ problems, live cancer, and cancer of the upper gastrointestinal tract.

Certain East Asian groups have a mutation in their genetic code that makes their bodies much quicker at converting alcohol to acetaldehyde.  Unfortunately, a large percentage of this group also have a genetic mutation that makes their bodies very slow at converting the acetaldehyde to acetic acid.  Thus, this group is susceptible to hangovers that begin shortly after they begin drinking and last for quite a long time.  For this reason, people who have these particular genetic mutations tend to be very light drinkers, if at all.

A similar type of effect can be produced with the drug Antabuse, which prevents acetaldehyde from converting to acetic acid, so the acetaldehyde stays in your system longer, which typically results in a severe hangover.  For this reason, Antabuse is often used by alcoholics to help quit drinking.

One common myth is that headaches experienced during a hangover are partially caused by alcohol killing brain cells.  In fact, the levels of alcohol one can consume, and live, are insufficient to kill brain cells.  You can read more on this here: Alcohol Does Not Kill Brain Cells

Other Contributing Factors:

  • Alcohol consumption also reduces the liver’s ability to effectively remove acetaldehyde and various other toxins from your bloodstream.  This can have various negative effects on your body, depending on the other substances present in your system.
  • Alcohol reduces the liver’s ability to compensate for dropping blood glucose levels by inhibiting the liver’s ability to produce glucose.  This results in the brain and your body getting insufficient glucose (the primary energy source for the brain, among other things), which will make you feel fatigued, moody, and weak.  This will also inhibit your ability to concentrate.
  • Significant alcohol consumption will also depress your central nervous system.  Once the alcohol has been processed by your body, this results in your nervous system going into a hyperactive state, which can cause you to have a rapid heartbeat and be shaky.
  • The alcohol itself will irritate your stomach and intestines.  This may result in abdominal pain, nausea, diarrhea, and vomiting.  The latter two listed will also further dehydrate your body.
  • Alcohol also interferes with normal sleep patterns, further contributing to the fatigue you may feel from a hangover.
  • Alcohol can also widen blood vessels, further contributing to a headache.

If you liked this article, you might also enjoy our new popular podcast, The BrainFood Show (iTunes, Spotify, Google Play Music, Feed), as well as:

Bonus Facts:

  • “Hangover” was a common term in the 19th century meaning “unfinished business”.  Around the early 20th century, the common meaning shifted slightly to mean as it does today.
  • As you get older, your body also has less alcohol dehydrogenase available for converting acetaldehyde to acetic acid.  Because of this, most people experience more severe hangovers later in life.
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  • Actually….

    It is the removal of electrolytes from your body that are more difficult to replenish than just water or fluids. Best way to ensure you don’t get a hangover? Go to the drug store and buy Electrolyte pills. Take before drinking, and after drinking before sleep.

    • Daven Hiskey

      @B: Loss of electrolytes is thought to be a contributing factor, but not as much as dehydration, and certainly not as much as the presence of acetaldehyde, which many researchers think is by far the biggest cause of most of the symptoms.

  • I have never had a hangover in my life, although I did wake up with a desire for a 2 Big Macs on the day after my 21st birthday. Not a good idea and I haven’t had a Big Mac since. Ugh.

  • If only I would have known about this in my college days!!!!!

  • Alcohol sucks– LEGALIZE POT

  • I also heard that a hangover is a kind of hypoglycemia crisis. The alcohol is transformed into sugar so that the body can absorb it. When you drink alcohol, your body will transform it, and then will have to deal with more sugar than what it’s used to. When the body has transformed all the alcohol and used up all sugar, you will go from “a lot of sugar in the blood” to “regular sugar rate in blood”. The body sees it as lack of sugar. Hence hypoglycemia crisis. You will then throw up, have headaches and all. (I apologize for my bad english and this kind of childish explanation, I don’t know molecules names in english or specific medical terms) (Sources are informal, explanation recieved at a hospital by nurses)

  • Hangover? What is this hangover you speak of?
    Seriously though, with all the problems I do have with my anatomy it is a wonder to me that I have never had a hangover.

  • It is absolutely dehydration. I had a bad case of the flu and was leaking fluids out of every orifice in my body for two days. It took two IVs of Ringers (which they almost could not get into my collapsed veins) to get me to feel like a human again. I crawled into the clinic and after I got my fluids back I walked out feeling the bomb. Unfortunately doing what you need to DRINK, when your body is telling you not to is easier said than done.

  • Dehydration sucks. I once had a nasty case of flu and had it coming out of every orifice. By the next day I felt so badly that I could not walk and literally just wanted to die. I tried to drink but when you are sick like that it is impossible. I went to the hospital where they said I looked green, they could not stick an IV needle in me as I had no water volume and my veins collapsed. When they finally did, after the first liter of Ringers’ I felt like a new man. It was incredible. But scary. You know what you need to do but you are so sick you can’t do it