‘Tis the season to be jolly…and hungover.

Humans have been consuming alcohol and suffering the aftereffects since before the beginnings of recorded history (9,000 year old Chinese pottery has shown alcohol residues), yet curiously enough, we still don’t fully understand the underlying causes of a hangover. The best science can do is identify a number of effects that come into play. The net combination of these effects, which will vary from person to person, make up the distinctly unpleasant experience we call a hangover.

In the U.S. it is estimated the economy loses approximately $148 billion dollars of annual economic output due to hungover people missing work, or working at a reduced capacity.

In this brief article we’ll look at three main areas – hangover symptoms, causes and remedies.

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Identifying the symptoms of a hangover is easy, as they are so obvious and so clearly linked to overindulgence in alcohol. However, it is very interesting that the symptoms can vary greatly from person to person, directly reflecting the fact that many different effects are at play. But without going into too much detail, the most common hangover symptoms include:

  • Headache
  • Nausea
  • Fatigue
  • Gas
  • Constipation
  • Irritability
  • Sensitivity to light
  • Sensitivity to noise
  • Reduced motor function
  • Lack of balance
  • Dehydration / thirst
  • Vomiting and / or diarrhea
  • A commitment to never drink alcohol again!

Indeed, reading through the symptoms makes a person wonder why we drink at all, or at least a second time! Perhaps a form of amnesia is at play too, although on a more serious note, it’s no secret that alcohol is an addictive substance, so no doubt we remember all too well the discomforts of a hangover but nevertheless feel compelled to drink again, even if the addictive effect is at an extremely low level.


Most elements of a hangover are a direct result of the body metabolizing the ethanol in the alcoholic beverages consumed. Breaking down ethanol is a nasty job, and it happens at a cost. Most of the work is done in the liver via oxidation, by two enzymes: alcohol dehydrogenase and aldehyde dehydrogenase. Without getting into too much detail, the process requires the conversion of nicotinamide adenine dinucleotide (NAD+), an oxidizing agent found in all living cells, into its reduced form, NADH.

When large quantities of alcohol are consumed and broken down, an excess of NADH builds up in the liver; for every molecule of ethanol metabolized, two molecules of NADH are created. The body requires NAD+ to survive. Faced with a shortage of NAD+ and an excess of NADH, the body diverts pyruvate that would otherwise be used to produce glucose, and uses it to create NAD+ instead. This results in severe shortages of glucose. Glucose is the primary energy source for the brain, so with a brain running on empty the hungover person can experience various cognitive impairments such as tiredness, inability to think properly, etc., plus a bad headache.

The first product of the metabolization process is acetaldehyde, also known as ethanal. It is approximately 10 to 30 times more toxic than alcohol, and is also a carcinogen and a mutagen. The acetaldehyde then breaks down further into acetic acid, which is harmless. The fermentation process used to create alcohol does this in reverse – converting pyruvate to acetaldehyde to ethanol.

An interesting side note involves those people of Asian descent who flush upon drinking alcohol, and experience hangover symptoms a very short period of time after drinking alcohol. They have a mutation in their alcohol dehydrogenase gene that causes their livers to convert ethanol very efficiently to acetaldehyde, but very inefficiently from acetaldehyde to acetic acid. This means they experience a very quick build up of acetaldehyde in their livers, and as a result they usually avoid alcohol, as the experience is very unpleasant. Sometimes alcoholics are prescribed a drug called disulfiram, which hampers the conversion to acetic acid, mimicking the Asian mutation’s effect of acetaldehyde buildup.

But to get back to the point, acetaldehyde is an extremely nasty substance, and its presence during the metabolization period, which can last for several hours, is a source of many of the hangover symptoms.

There are other chemical disturbances caused by the introduction of alcohol into the body. Generally speaking they involve the temporary presence of a variety of toxins and free radicals that produce negative effects of a lesser magnitude than those described in the previous paragraphs, but nonetheless certainly contribute to the hangover experience. Some effects may last longer. For example, the body’s metabolization of ethanol uses vitamin B12 as a coenzyme, therefore a drinking binge, or prolonged periods of regular drinking, can leave a person with a vitamin B12 deficiency. This vitamin is extremely important to a person’s health, particularly to the brain and nervous system.

EEGs show reduced brain wave activity up to 16 hours after all physical remnants of alcohol have left the body. It has also been shown that neuromuscular performance is impaired long after the last trace of alcohol has left the blood.

Another aspect involved in the metabolization of ethanol is an increase in urine production. In other words alcohol is inherently a diuretic. Drinking alcohol results in a net loss of water by the body, and creates the numerous side effects of dehydration, which become increasingly apparent as water loss levels get above the 2% mark. Many, or most, of the symptoms of hangovers are caused by or enhanced by dehydration, including headache, dry mouth, constipation, etc.

The human stomach is not designed to absorb large quantities of alcohol. Well, in fact I think you could say it’s not “designed” to process alcohol at all, but small amounts don’t cause it much problem. However, as the volume increases, the likelihood of the drinker experiencing nausea rises. I would say (with absolutely no evidence to back me up) that it would be very difficult to separate the physical reaction of the stomach to large amounts of alcohol, from the subconscious mental reaction. Surely after a few hours of heavy drinking, the brain is sending signals to the stomach, “This is not good for you, expel, expel!”

Another hangover effect that can last for a day or two longer than the initial recovery is related to alcohol’s depressive qualities. This takes us to a point that is beyond the intended scope of this article, which is a lighthearted look at hangovers. However, if a person drinks excessively, it will have an effect at the neurological level. The body’s attempt to deal with this disruption of its normal neurological functions will almost certainly result in some temporary imbalances until things stabilize again. It is very common for hungover people to experience mood swings, or changing levels of confidence – certainly a disturbing part of the package! Some scientists believe that hangovers symptoms are actually withdrawal symptoms.

Another facet of hangovers involves allergies. Many alcoholic drinks contain impurities that give the drink its unique character. For example, whiskies contain all sorts of diff e re n t compounds that have leached out of the oak barrels the whisky is aged in. These substances have widely differing qualities, but have been lumped together under the name congener. They include histamines, tannins, metals, aldehydes and methyl alcohol. Generally speaking, the darker or more flavourful the drink, the higher the level of congeners. Many of these substances trigger allergic reactions in some people. The re a ctions vary from person to person, but typical ones are headache and stuffy nose / sinuses. General congestion can lead to typical symptoms such as headaches, impaired vision, and degraded balance. Drinking purer drinks (i.e. low levels of congeners) such as vodka can minimize these eff e c t s .

Lastly, there is an often overlooked component to hangovers, overlooked because it is not necessarily directly connected to drinking alcohol. That is sleep deprivation. Many people keep fairly regular hours in terms of when they go to sleep and wake up. Social events involving drinking often throw that schedule completely out the window, with people staying up far later than usual. Doing this puts the body out of synch with its natural circadian rhythms – in essence, the person experiences jet lag symptoms such as headaches, sleeplessness, loss of appetite, without ever travelling anywhere. To test this, try staying up really late and just drink water – odds are you will feel not so great the next day or two. Compounding this effect is the likelihood that all the other hangover symptoms will prevent a good sleep when you do get to bed after a night of drinking.

To wrap up the section on hangover causes, I’d like to elaborate on my earlier comment that, “….we still don’t fully understand the underlying causes of a hangover.” In fact, science does understand the entire cocktail of causes and effects at play, but it may be said that the difficulty in pinpointing the exact causes of hangover symptoms lies in the fact that there is so much overlap between the various causes’ symptoms, and each person’s hangover is a bit different. But at the end of the day (or maybe night is more appropriate), does it really matter whether your headache is caused by the presence of acetaldehyde in your system, or dehydration, or hypoglycemia, or lack of sleep, or any of the myriad effects of drinking alcohol? The bottom line is that alcohol = hangover.


There is no shortage of hangover cures, and most of them are probably ineffective, or totally bogus. However, for what it’s worth, here are some recommended hangover cures:

  1. Abstinence! This is the only sure fire way to cure a hangover – don’t get it in the first place. “No compelling evidence exists to suggest that any conventional or complementary intervention is effective for preventing or treating alcohol hangover. The most effective way to avoid the symptoms of alcohol induced hangover is to avoid drinking.” (Pittler, British Medical Journal)
  2. Hydration. If a person can drink water in between alcoholic drinks, then they will not become as dehydrated. During the recovery period, especially just before going to sleep, drinking water will help the body rehydrate. The body needs the fluids to be able to more effectively flush the waste products created by the breakdown of ethanol.
  3. Exercise. Some light exercise will speed up the body’s metabolism. The higher levels of blood flow and higher levels of oxygen circulating through the body should help speed up the metabolization of the alcohol, and the flushing of toxic waste products from the system.
  4. Consumption of certain foods. The ingestion of calcium, cysteine, and vitamin C has been shown to help alleviate hangover symptoms, so any foods or drinks containing these should help. A good example would be an early breakfast of eggs and orange juice.
  5. Sleep. Sleep may or may not help cure a hangover, but at the very least while one is asleep the discomforts of the hangover are not consciously experienced.
  6. Pain killers. Over the counter pain killers can certainly help reduce headache pain, plus other symptoms such as sore and tired muscles. Some of them are hard on the stomach though.
  7. Oxygen. Some medical studies have shown that breathing in oxygen alleviates hangover symptoms. I’m skeptical.
  8. Stick to your sleep schedule. This will minimize the sleep deprivation / jet lag effects.
  9. Food. Eating before and at the same time as drinking alcohol will slow down the absorption of alcohol into the blood and onward to the liver. This allows the body to stay more balanced neurobiologically as it breaks down the alcohol over a longer period of time. Drinking on an empty stomach, and / or not eating while drinking alcohol results in the body coping with a huge onslaught of alcohol, and the hangover symptoms are likely to be worse.

There is no shortage of other “remedies” to hangovers, and they are simply too numerous to list here. A quick search on the Internet will yield all sorts of hangover cures. Some are no doubt partially effective, others are downright ridiculous, and the rest fall somewhere in between. I think the deal is if you drink alcohol, you will pay the price; if you have a hangover, treat the symptoms as best you can. Good luck!



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