How much alcohol is needed to cause dehydration?

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Frank Wals

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How much alcohol is needed to cause dehydration?
« on: 13/01/2011 17:30:03 »
Frank Wals  asked the Naked Scientists:
Dear Chris,

I'm a new fan of the show and wanted to thank you for all the lovely insights so far. I also have a question:

We always hear that drinking alcohol dehydrates a person very much and that you always need to drink water to compensate. On the other hand I learned that during the Middle Ages people in big European cities drank beer rather than water, because the water was so mucky and unhealthy. How could they drink beer all day and not completely dehydrate?

I've considered three possible answers:

1. Beer does not withdraw fluid from the body. (I've had a few hangovers to know this is false.)

2. People during the Middle Ages did not drink as much beer as we are made to believe, or they drank some lemonade on the side.

3. Beer back then did not contain enough alcohol to dehydrate a person. In other words there was enough water in the beer to keep one in shape.

What's the solution? And if answer 3 is correct: What is the approximate ratio alcohol/water to keep a person fit?

Kind regards,

Frank Wals
Utrecht, The Netherlands

What do you think?
« Last Edit: 13/01/2011 17:30:03 by _system »


Offline Mazurka

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How much alcohol is needed to cause dehydration?
« Reply #1 on: 14/01/2011 16:48:26 »
1) you're right it definitely does.  Some silly friends of mine tried to measure the extra volume of liquid excreted vs consumed and found that you excrete around 1 1/4 to 1 1/2 times more than you consume of "normal" beer.

2&3) beer is generally stronger now than in the middle ages - which may be a major effect.

water is also consumed in other ways such as in food and assuming it has been hot enough such as in the oven or the stewpot bugs will have been killed.