Does drinking alcohol actually cause dehydration?

alcohol-effects

Today I came across this article: Drinking water doesn’t prevent a hangover, study says, which includes the memorable line: “[the] study concluded, the only way to prevent a hangover is to drink less alcohol.”

Now, at first sight, you might think that surely this simply another piece of work from the University of the Bleedin’ Obvious.

But hang on. Alcohol does dehydrate you, doesn’t it? Everyone knows that! After all, don’t you wee more when you go drinking, and wake up all sweaty and with a dry mouth after a ‘heavy night’? Surely this is all evidence of fluid loss? Am I really about to suggest we should consign ‘alcohol causes dehydration” to the collection of alcohol-based myths such as mixing drinks gives you a worse hangover (only if you drink more as a result), a night cap will help you sleep (only temporarily, overall it tends to disrupt sleep), drinking beer will cause a ‘beer belly’ (too much of any type of drink can cause weight gain), and so on?

Well…

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There are many alcohols; ethanol is the one we drink.

Firstly, what is alcohol or, more specifically (the word ‘alcohol’ actually refers to a group of compounds), ethanol? It’s a simple molecule, containing only two carbon atoms, an oxygen and some hydrogen atoms. It’s produced, as we all learned at school (or possibly when attempting home-brewing), by yeast during the process of fermentation. Feed this clever little single-celled organism some sugar and voilà, it produces ethanol (C2H5OH) and carbon dioxide via a remarkably simple equation:

C6H12O6 –> 2C2H5OH + 2CO2

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Marula fruit naturally ferments.

Humans learned this trick a long time ago and have been brewing for literally thousands of years. In fact it doesn’t even require human intervention – marlula fruit is particularly famous for becoming naturally alcoholic (although stories of monkeys and elephants using it to get drunk might be somewhat exaggerated).

We like drinking because, of course, of what it does to us. In medical terms, it’s a central nervous system depressant with significant psychoactive effects (sounds fun, eh?) In English, it reduces anxiety, making drinkers feel relaxed and happy. This accompanies a decrease in motor skills of course, which is why drinking and driving is illegal virtually everywhere (although exact definitions of what this means do vary).

But while alcohol is all natural, it’s not what you’d consider healthy. Every now and then someone drags out some data that suggests that low to moderate alcohol intake is good for you, but this sadly appears to be more wishful thinking than good science. In terms of disease, alcohol consumption has been linked with stroke, high blood pressure, several liver diseases, pancreatitis, a weakened immune system and a handful of cancers including mouth, throat, liver and breast cancers.

In fact, alcohol has been categorised by the International Agency for Research on Cancer as a group 1 carcinogen, which puts it in the company of such other delights as asbestos, radium isotopes, ultraviolet radiation, diesel exhaust and tobacco.

Enjoying-Dinner-copy

Give up alcohol before you worry about your latte ingredients.

Of course, the dose makes the poison. Lots of people enjoy low to moderate alcohol consumption quite safely. Still, I have to admit to being amused by health nuts that insist on a diet consisting of little more than raw vegetables, make a fuss about so-called GMOs, campaign for additives (none of which are anywhere close to being group 1 carcinogens) to be removed from food, and then post pictures of themselves drinking wine. You really want to improve your health? Never mind caramel colour IV in your latte, give up the booze.

So, alcohol isn’t a health food, or indeed drink. But to get back to the original question, does it cause dehydration? Well, it would appear that while it does do a lot of bad stuff health-wise, that’s not one of the bad things it does. In a study, men drank six pints of beer and were then subjected to a number of tests. As the subsequent PubMed article states: “All subjects had a slight hangover, but none was fluid depleted”.

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Twin doctors Chris and Xand van Tulleken in a recent BBC documentary.

In a recent BBC Horizon documentary, twin doctors Chris and Xand van Tulleken collected all their urine during a night in which Xand drank 21 units of alcohol in one sitting (while his brother only had one drink), and next morning demonstrated that the volumes were the same. In other words, the excessive alcohol consumption had not, as is widely believed, had a significant diuretic effect.

Admittedly, this was only two people, and the PubMed study only involved six participants – small sample size is often an issue with such work. The Dutch study I mentioned at the start was much larger, which is one reason it’s useful. In that study, drinking water appeared to make little difference to the severity of the hangover experienced. The only thing that really mattered was, not surprisingly, how much alcohol had been consumed.

In fact it’s not well-understood what does cause hangovers. It would appear it’s linked to an immune system response. In very simple terms, getting blind drunk is a little like self-imposed flu. Drinking plenty of fluids won’t do you any harm, but it’s not actually a solution. Of course, there’s no virus involved here to keep the immune system on the warpath, so for most healthy people the best, and probably only, hangover cure is time.

So in summary, yes, we probably can chuck “alcohol causes dehydration” in with all the other alcohol myths floating around out there, but that’s not an excuse to have a pint after your workout.

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