What’s in a Hangover?


“Why do I have a hangover?” is a question most of us have asked at some time (hopefully not too often). The most basic answer is in two parts: a) there was ethanol available, and b) you drank more of it than your body was comfortable metabolising from the time that you started drinking up until you realised that you had a hangover. There may be many factors which made drinking to this extent an option for you (social/cultural, psychological), but analysing them is not going to help you if you’re actually suffering at this point in time (and I genuinely hope that you’re not).

Before looking at what’s behind hangovers I’d like to share a personal theory: the optimum level of inebriation is at the point at which you finish your second pint (of something 4-5% abv). At this moment people are usually hydrated/refreshed by beer, relaxed, sociable, less inhibited but not to the point of doing something regrettable, and possibly even the scintillating company that they think they are. At this point, people tend to head to the bar for pint #3, confident that they can simply keep topped up and maintain their gentle alcoholic euphoria.

They’re probably wrong. In the UK, one ‘unit of alcohol’ equates to 10ml of ethanol, and this is approximately the amount of booze a healthy adult can process in the space of an hour. If we say that someone spent an hour drinking their two pints (it was probably less), as they slam that second empty glass down and head to the bar, they will have (2 x 25ml = 50ml, -10ml for the unit their liver has processed in the hour, and rounding a pint down to 500ml) 40ml of alcohol swilling about in their system waiting to take effect, so by the time they get stuck in to #3 they are already considerably further down the line than they might think, probably with impaired judgment, and could (but not necessarily) be heading into a different state of inebriation altogether. Note also that because there is a different distribution of body fat and water in men and women (men have more water in comparison to fat), and because alcohol distributes in water, the same quantity of alcohol will have a greater physiological impact on a woman than a man. In a sense a given volume of alcohol is experienced in a more diluted form in a man’s body than it is in a woman’s.

So what about the hangover then? This probably breaks down into three main areas: dehydration, a toxic and over-worked liver, and related tiredness. An understanding of how the body breaks down ethanol will help understanding all this, but if you want to jump ahead a look at some ‘interventions’ by all means go ahead.

bloody mary

Ethanol Metabolism

Ethanol does not need to be digested – it can be absorbed into the blood stream as it is. The main place this happens is in the small intestine, but it can also be absorbed in the stomach (less so if the stomach is busy with food). Once it’s whizzed around your body a few times doing what it does, it ends up in the liver where it’s broken down, eventually into something more manageable and less toxic.

Alcohol goes through four phases before the body is done with it and the by-products can be breathed out (as CO2) or peed out. Most of the action takes place in the liver, and a messy trail is left behind which the liver itself has to clean up. If you embark on a heavy evening’s drinking you’ve basically asked your liver to pull a double shift. It was hoping to get dinner out of the way and settle down to a nice rest, but instead it is pumping enzymes at the booze you’re throwing at it, and will now spend the night rallying antioxidants to deal with the aftermath. No wonder it’s grumpy, plus this work going on inside you will disturb your sleep (even if you’re unconscious, it will not be good-quality down-time) adding to the feeling of overall roughness.

The first phase is ethanol to acetaldehyde. Anyone who’s brewed an ale in hot weather will know what this smells like, as it is a by-product of the early stages of fermentation, particularly at higher temperatures. It gives a ‘green apple’ smell and drinking a beer with detectable levels of acetaldehyde is not that pleasant. Fortunately, yeast will often clean up this flaw if left to rest (‘in ruh’) for a day or two once primary fermentation has finished. There are a couple of classes of enzymes which break down ethanol into acetaldehyde, but the main ones are the various alcohol dehydrogenases (ADHs). Acetaldehyde is nasty stuff which binds readily with the proteins in your body, changing the way they work – and not for the better. These changes do not always reverse, and the product of acetaldehyde plus protein can even stimulate an immune response, leading to even more work for your body. In a nutshell, acetaldehyde does horrible things to the cells in your body and contributes to a toxic hangover feeling.

By the way – if you’ve read this far, you probably don’t have a hangover.

The second phase is the breakdown of acetaldehyde to acetate. Aldehyde dehydrogenases (ALDHs) are the enzymes responsible for this, but genetically not everyone produces these in the same quantity. If you’re not producing enough ALDH to cope with the acetaldehyde in your system then it can lead to a ‘flushed’ look. Acetate is largely processed outside of the liver, but the route to producing it will have left your liver oxidised, toxic and tired.

The third phase sees acetate broken down into stuff called Acetyl Co-enzyme A (AcetylCoA), which the body can process into water and carbon dioxide without much extra wear and tear in the four step to complete ethanol metabolism.

So metabolising ethanol accounts for the tiredness and the toxic feeling, so what about dehydration? Beer is usually over 90% water so how come drinking it can make you dehydrated? The problem is that once it reaches a certain level ethanol suppresses the body’s production of Anti-Diuretic Hormone. In a long night of drinking you might hit that level and then stay there, meaning your body will be repeatedly telling you to go to the loo, even if strictly speaking you don’t need to expel that water. This leads to you losing more fluids than you gain and hence dehydration.

Some Interventions?

So – apart from the obvious (not drinking, or at least not drinking to excess) how can you avoid or cure a hangover? According to the British Medical Journal there is significant reduction in hangover symptoms (“headache, laziness, and tiredness”) in subjects taking one or other of borage, artichoke or prickly pear food supplements, or [B-vitamin heavy] yeast preparations. However, the BMJ says that these are not cures as such.

Taking the food supplement N-Acetyl Cysteine also seems to help. It is a precursor to the antioxidant glutathione – important stuff for cleaning up the trail of devastation left by acetaldehyde metabolism – and is available in some high street health food shops as well as on the internet. The snag is you have to remember to take it before going to bed to get the most benefit from it. Eggs are a good natural source of N-Acetyl Cysteine. I’ve tried N-Acetyl Cysteine and found that it does make a difference.

Others swear by milk thistle extract, but I hear that it makes you pee every five minutes. This might explain how it flushes out toxins, but would not appear to help with a restful night’s sleep.

A cleansing ale, or similar ‘hair of the dog’ approaches are certainly ways of changing a hangover into something else but I’m personally not sure if they ‘cure’ a hangover as such…

Regarding hydration – unless it’s taken with food drinking plain water might not be the best idea as it can actually draw sodium and potassium out of your body proper and into the gut. Ideally if you’re dehydrated you want rehydration salts such as Dioralyte. At a push a 50/50 mix of fruit juice and water with a pinch of table salt could be used, but it’s not ideal and you shouldn’t drink more than a pint or so of it.

Disclaimer – nobody is suggesting that you should try any of the above, or that they will actually make a difference to a hangover. Before taking food supplements you should check for any contraindications and consult a medical professional if you are unsure.

With this disclaimer in mind, and with the thought that we at UKCBN do not want you to go out and get smashed just to test these or any other interventions, what do you find works for a hangover?


As well as some rather old undergraduate physiology notes, and a thumbed copy of a New Scientist special edition on alcohol (issue 2214, Nov 27 1999), the followed helped with the scientific bits of this post:

Koskinas, J. (2002) ‘Acetaldehyde Adducts: Role in Ethanol-induced Liver Disease’ In. Sherman, D. I. N., Preedy, V. & Watson, R. R. (eds.) Ethanol and the Liver: Mechanisms and Management. London and N. Y.: Taylor and Francis. pp. 130-149.

Kwo, P. Y. & Crabb, D. W. (2002) ‘Genetics of Ethanol Metabolism and Alcoholic Liver Disease’ In. Sherman et al.

Pittler, M. H., Verster, J. C. & Ernst, E. (2005) ‘Interventions for Preventing or Treating Alcohol Hangover: Systematic Review of Randomised Controlled Trial’ BMJ: British Medical Journal 331(7531) pp. 1515-1517

You could also search ‘alcohol’, ‘hangover’ etc. on the New Scientist web site for more info, but at the time of posting the content seems to repeat that presented above.

At least none of the above is some old rubbish blown in on the winds of Google or ruddy Wikipedia!


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