WASHINGTON The notion that guzzling glasses of water to flood yourself with good health is all wet, researchers said on Wednesday.
Dr. Stanley Goldfarb and Dr. Dan Negoianu of the University of Pennsylvania in Philadelphia reviewed the scientific literature on the health effects of drinking lots of water.
People in hot, dry climates and athletes have an increased need for water, and people with certain diseases do better with increased fluid intake, they found. But for average healthy people, more water does not seem to mean better health, they said.
Their scientific review, published in the Journal of the American Society of Nephrology, is the latest to undercut the recommendations advanced by some experts to drink eight glasses of 8 ounces (225 ml) of water a day.
Dr. Heinz Valtin of Dartmouth Medical School in 2002 also put those recommendations to the test, finding them to be more urban myth than medical dogma and lacking in scientific basis.
Goldfarb and Negoianu examined what Goldfarb called "four major myths" regarding claims of a benefit for extra water drinking: that it leads to more toxin excretion, improves skin tone, makes one less hungry and reduces headache frequency.
"Our bottom line was that there was no real good science -- or much science at all -- behind these claims, that they represent probably folklore," Goldfarb said.
As far as facilitating toxin excretion, Goldfarb said that was not verified by any sort of scientific study.
"The kidneys clear toxins. This is what the kidneys do. They do it very effectively. And they do it independently of how much water you take in. When you take in a lot of water, all you do is put out more urine but not more toxins in the urine," Goldfarb said.
No studies showed any benefit to skin tone as a result of increased water intake, they found. They also found evidence lacking that drinking water wards off headaches.
As far as lots of water serving to limit appetite, he said there was no consistent evidence, adding it was "a little unclear exactly whether that was true."
"What no one looked at is whether anyone really loses weight over the long haul if they go under this regimen of drinking lots of water," Goldfarb said. "We just expressed uncertainty in that area."
While it may not help a person to drink lots of water, it may not harm them much either, Goldfarb said.
"If someone enjoys it, I say that's wonderful, keep doing it. They're not doing anything that's going to hurt them."
"A little mild dehydration for the most part is OK, and a little mild water excess for the most part is OK. It's the extremes that one needs to avoid," he said.
(Editing by Maggie Fox and Peter Cooney)