Researcher pours cold water on 8-glasses-a-day fad

The only health benefit from drinking eight full glasses of water a day may come from running to the bathroom, a researcher has suggested.

Newspaper articles, health and beauty magazines all advise drinking at least eight full glasses of water a day for optimal health.

But Dr Heinz Valtin of Dartmouth Medical School in New Hampshire said his 10 months of research found no scientific evidence to back up this advice, which has helped create a huge market for bottled water.

Writing in the American Journal of Physiology, Dr Valtin, a kidney specialist, said food contained some water.

The Food and Nutrition Board of the National Research Council has recommended drinking about one millilitre of water for each calorie of food eaten. This adds up to 2 litres, on an average 2000-calorie diet. But the council also noted that much of this is already contained in food.

"I did 43 years of research on the osmoregulatory system. That system is so precise and so fast that I find it impossible to believe that evolution left us with a chronic water deficit," Dr Valtin said.

If a person gets low on fluid, the body compensates by bringing fluid back out of the kidneys and by slowing the loss of water through the skin, Dr Valtin said. Thirst kicks in long before dehydration starts.

He and colleagues became concerned after seeing dozens of newspaper and magazine articles urging people to sip water all day.

The journal asked him to review all the scientific studies he could find and he concluded that someone misinformed has been telling people to drink large amounts of water "Persons with certain diseases must have large volumes of water - kidney stones are probably the most common example," Dr Valtin says.

The rest can just drink enough to slake thirst - and this includes coffee, tea, and even beer.

He hopes people will be relieved of the guilt of not getting enough water, and of the expense of buying bottled water.

"There is also the possibility that if you drink a lot of water that happens to be polluted then of course you get more pollutants.

"Then there is the inconvenience of constant urination, the embarrassment of having to go to the bathroom all the time."

Overdosing on water can lead to confusion and even death. Water intoxication is one deadly effect of taking the drug Ecstasy because it provokes overwhelming thirst.

- REUTERS

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