Thursday, July 10, 2003

A watery grave

'Are you in danger of a water overdose?', asks the UK Mirror newspaper. Apparently, there are some people drinking too much water and apparently putting their lives at risk. For example, actor Anthony Andrews was rushed to hospital after drinking eight litres of water to combat the heat on-stage, while performing in My Fair Lady. A more famous example is that of Leah Betts, the teenager who died after taking ecstasy, but whose death was largely the result of consuming too much water to counteract the effect of the drug. How much should we drink? The Mirror says, 'Although there are no recommended limits...it's generally thought that it's safest to stick to no more than three litres in one day.'

This is a panic inspired by a panic. For years, we have been told by health 'experts' that we don't drink enough water. As the Mirror story notes, 'Some experts claim dehydration is to blame for everything from heart disease and cancer, to asthma and depression'. It is a fine line between drinking the two litres of water we supposedly need, and the three litres which could potentially kill us.

But, as Professor Heinz Valtin wrote in the American Journal of Physiology in 2002, it is 'difficult to believe that evolution left us with a chronic water deficit that needs to be compensated by forcing a high fluid intake'. In other words, our bodies are extremely good at controlling the amount of water in our blood at any time. While 'water intoxication' is possible, it is also very rare. If we drink too much, we are likely to spend rather longer than we need going to the toilet, but that's about it. A radical solution might be to suggest that people should drink some water when they feel thirsty. But where's the public health education programme in that?

One good thing about this story is that it puts the whole discussion about the poisons of modern life into perspective. There is no such thing as a poisonous substance, per se. Even drinking water can kill you, if you drink enough of it. It's the dose that makes the poison.

Are you in danger of a water overdose?, Mirror, 10 July 2003

Drink at least eight glasses of water a day for better health?, American Physiological Society, 12 August 2002

Star's water overdose, Sky News, 4 July 2003

Leah Betts died of drinking water to counter drug's effect, The Times, 22 November 1995, reproduced on Urban75 website

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