We would be more productive if we drank less - water

There is little if any scientific evidence that drinking two litres of water a day has any health benefits

SO, ANOTHER modern health myth has bitten the dust. You don't have to drink eight glasses of water per day, if you don't damn well feel like it. Last week Glasgow GP Margaret McCartney examined the claim that drinking eight glasses of water per day was beneficial, and concluded that it was "thoroughly debunked nonsense". On the contrary, Dr McCartney wrote in the British Medical Journal, drinking too much water can actually be harmful. Here was a shot that went round the world. There hasn't been this much excitement since it was established that the American recommendation to "Strive for five" servings of fruit and vegetables every day had been arrived at pretty much at random.

It is extraordinary how obedient we, the worried well, continue to be. Many people – possibly millions – were trying to drink eight 8oz glasses of water per day, which is pretty much two litres. No wonder we never get anything done.

There is the brilliant New Yorkercartoon of two shambolic drunks sitting at a bar, with the fumes that drunks always have in cartoons radiating from them, and one drunk is saying to the other – I'm paraphrasing here: "And I'm still getting my eight glasses of water a day."

These health slogans enter our culture with amazing ease, penetrate it on every level, and are never seriously questioned.

And these little mantras, as that cartoon showed, become magic spells that somehow protect us from, er, everything. But most disturbing of all, probably, is the seriousness with which all this nonsense is promoted.

Last week on various American websites people were remembering the dread warning – and I myself remember this from the health pages of women’s magazines: “If you only drink when you’re thirsty, it’s too late.” As one commenter put it, then there was the flash of lightning and the drum roll, before you died screaming from not buying enough bottled water.

But far from having to force this volume of water down our gullets, Dr McCartney says: “If you’re drinking excessively, if you’re drinking beyond thirst; if you’re drinking beyond comfort, your kidneys are actually having to work very, very hard.” This is not a solo run by Dr McCartney – far from it. The Mayo Clinic has stated that the recommendation to consume eight 8oz glasses of water per day “isn’t really supported by scientific evidence”. Our excretory aim, according to the Mayo Clinic, should be to produce “ six cups of colourless slightly yellow urine per day”. Only six cups – no wonder they get so much done at the Mayo Clinic! But then, the American measuring system, which uses the cup as a unit, can be a bit confusing, as anyone who has tried to follow a Betty Crocker recipe will tell you.

Our own William Reville was writing about the inadvisability of drinking large amounts of water in this newspaper in March 2009. He was reporting on work that had been published two years before, in the British Medical Journalof December 22nd, 2007. In it RC Vreeman and AE Carroll explored seven myths of medicine. They started with the over-consumption of water and moved on to other beliefs commonly held by the general public, which look now less and less like the beliefs of an adult population and more and more like the urban myths passed on by teenagers: that fingernails grow after death; that shaving makes hair grow faster; that eating turkey makes you drowsy; that mobile phones cause disruptive electro-magnetic fields in hospitals. (Vreeman and Carroll found mobile phones were disruptive 1.5 per cent of the time. Which may seem quite a lot if you're on a heart monitor, I suppose.)

Unlike the other items on that rather sorry list, however, the high consumption of water is good business for some. Dr McCartney's research specifically targeted the recommendations of the Hydration for Health research body, which is backed by mineral water manufacturers Volvic and Evian. According to the radical American magazine Mother Jones, Volvic and Evian are owned by the huge food conglomerate Danone. To Mother Jonesthe bottled water story is one of capitalism gone mad – they note that the University of California spent $2 million on bottled water at its campuses in San Francisco and Berkeley at a time when it was laying off 2,000 staff. Tap water is good in these areas and San Francisco banned bottled water from the city government's offices some years ago.

And the more you think about it, the harder it is to disagree with this view. All those conscientious office workers with the plastic bottles on their desks, all those plastic bottles going to landfill, all the gym girls glugging their way through their work-outs – we have all been had. They told us it was science but it was commerce all the time. Just as the fizzy drink Lucozade was once sold to us as a drink that doctors prescribed in hospitals, on the grounds of its magic ingredient, glucose. Then it became “Lucozade: replaces lost energy quickly.” Now it is a sports drink. In modern times science is the big sell. But whoever would have guessed, in a million years, that water would be pushed on us in this way? It is a parable about our gullibility and their marketing genius. Dr McCartney says we would do just as well, and the environment would do much better, with the stuff that comes out of the tap.