WASHINGTON (Reuters Health) - A panel of scientific advisers met Monday to begin assessing the benefits and risks of water and electrolyte consumption, and said they will issue a report with new recommended intake levels in the spring of 2003.

Electrolytes are substances contained in water and other fluids, such as sodium, potassium and chloride, levels of which play an important role in a number of body functions.

The panel will explore, among other issues, the scientific underpinnings of the eight-glasses-of-water-a-day recommendation that has become a mantra among health officials, said Dr. Lawrence Appel, chairman of the Institute of Medicine's (IOM) Panel on Dietary Reference Intakes for Electrolytes and Water. Appel told Reuters Health that even he wonders where the number came from, and if it is appropriate for everyone.

The committee will also try to determine if there's any harm to excessive water intake, and if sports drinks and waters fortified with potassium, sodium chloride and sulfates provide benefits or undue risks.

The report is part of the IOM's Food and Nutrition Board's continuing effort to develop dietary reference intakes for food, nutrients and fluids. The government has issued recommended daily allowances for human consumption, but the IOM panel has been asked to more deeply assess the science and come up with a new set of recommendations, said Appel, a professor of medicine at Johns Hopkins Medical Institutions in Baltimore, Maryland.

Panelists will try to develop dietary reference intakes for water and electrolyte-fortified fluids for healthy people, pregnant and nursing women, and people who have chronic disease.

The available data is often lacking, however, said Appel, noting that many fluid intake studies have been conducted with just a handful of people. And other studies have been done by water and sports-drink makers, perhaps not always under the rigorous scientific conditions used in academic research.

Appel said new studies to address gaps may be conducted during the next year or so while the panel gathers information and formulates its opinions.

On Monday, committee members heard from Dr. John Greenleaf, a scientist with the National Aeronautics and Space Administration (NASA), who said that most Americans seem to be chronically under-hydrated. Studies he has conducted show that people will drink more water if it has a flavor or has added salt and sugar, but that it isn't clear yet if those fortified waters provide better hydration.

Another researcher and panel member, Dr. Oded Bar-Or of McMaster University in Hamilton, Ontario, Canada, said his studies have also shown that healthy children drank more water when it had both salt and sugar added.

But it is not known if those fluids have harmful effects.

The committee also heard data exploring how thirst is initiated and controlled. Dr. Edward Stricker of the University of Pittsburgh, Pennsylvania, said that the sensation of thirst is not well understood. "In fact, it is a very complex business," he said, adding that most of the basic studies delving into thirst and its role in human functioning have been done in rats, not humans.

Experts at the National Academy of Sciences will review the panel's report before it is issued to the public next year, said Appel.

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