The British Journal of Medicine is the latest to say that the popular belief that adults need to six to eight glasses of water daily is firmly rooted in myth.

There is a "complete lack of evidence supporting" the advice, said researchers writing in the Journal's latest issue. While nutritionists and dietitians recommend drinking lots of water for supposed health reasons, the Journal's researchers said that, in fact, the advice could be unhealthy.

Regardless, Americans continue to consume lots of water, especially the so-called "pure" stuff that's sold in plastic bottles. This despite admissions by marketers of Aqufina (Pepsi) and Dasani (Coca-Cola) that their water — costing up to $10 a gallon — comes straight from the tap and is little different than water available for nearly free in most homes.

Some health advocates warn that children drinking bottled water are often denied the dental benefit of fluoridation that comes in municipal water supplies but is generally lacking in bottled water.

But adults continue to guzzle overpriced water that's contained in an estimated 12.1 billion plastic bottles last year. Less than 15 percent of the bottles are recycled.

A number of city mayors, including R.T. Rybak of Minneapolis, have urged the U.S. Council of Mayors to undertake a review of the environmental impact of all those bottles. San Francisco and St. Louis have joined Los Angeles in prohibiting city funds being used to purchase bottled water.

The writers in the British Journal of Medicine cite what they called "an exhaustive" survey by nutritionist Heinz Valtin of the Darthmouth Medical School that found no basis for the advice to drink six to eight glasses of water daily.

Valtin said that with few exceptions, people get all the water they need from foods they eat and from water in a variety of common drinks like coffee, juices, milk and even beer.

Valtin's survey drew criticism when it was first published five years ago in the American Journal of Physiology. However, the National Institutes of Medicine later conducted an independent survey and concluded that Valtin's findings were correct.

Regardless, nutritionists have been slow to incorporate the science. Advice to drink up to eight glasses daily still comes from Weight Watchers, authors of diet books and, even, some health care experts, including those at the Park Nicollet Clinic in the Twin Cities.

Nutritionist and author Barbara Rolls told Runner's World magazine: "I remain skeptical of all these so-called dehydration problems. It's a myth that's being perpetuated."

Rolls added: "The thirst mechanism is exquisitely tuned to keep us in fluid balance."