More water better health: Where's the proof? Scientists ask

In findings to published in the June 2008 issue of the Journal of the American Society of Nephrology (JASN) , scientists state that there is currently little research into the field of how an average persons health is affected from extra fluid consumption.

"There is simply a lack of evidence in general," the authors stated.

The claims could come as a blow to some drink producers, particularly in the bottled water industry, which has seen strong sales increases across the globe on the back of the perceived health benefits of the product, highlighting the importance of obtaining clinical backing for a product.

Report authors Dr Dan Negoianu and Dr Stanley Goldfarb said that while water consumption is obviously vital to humans, there is less certainty about claims from experts linking hydration to maintaining healthy organs and skin.

In an attempt to get a better understanding of the potential health benefits, the researchers, both from the Renal, Electrolyte, and Hypertension Division at the University of Pennsylvania reviewed current clinical studies concerning the topic.

While the authors claimed to find evidence supporting some benefits of increased fluid intake with people carrying certain diseases, no single study concluded that there was a need to consume the recommended eight glasses of eights ounces - '8x8' - of water a day.

This led both researchers into questioning where the '8x8' recommendation originated.

However, they added that individuals in hot, dry climates and athletes did require increased water consumption.

Studies reviewed Studies included in the literature review included research into whether water intake improved kidney function and helped to clear toxins.

The researchers concluded that while testing did find water did impact on removing substances like sodium and urea from the kidney, no resulting clinical benefits were identified.

Other tests looked at how water consumption influenced organ function, particularly in regard to how quickly it was consumed in relation to water retention.

Regardless of how quickly or slowly water was drank though, there was not a single study that linked higher intake with organ efficiency, according to Negoianu and Goldfarb.

Other popular claims made about higher water consumption, including that it can curb appetite for weight loss and serve to improve skin tone, were also looked at by the researchers, though scientific support for these ideas was respectively not available and unsupportive.

The scientists did stress that dehydration could lead to skin turgour.

Additional research that attempted to test links between headaches and water deprivation was limited in its scope.

Although respondents who increased water intake were found to experience fewer headaches than those who did not, Negoianu and Goldfarb claimed the findings were not statistically significant.

Industry reaction A spokesperson for industry association the Bottled Water Information Office rejected claims that higher water consumption had no proven health benefits and said that it was widely accepted to be a vital part of nutrition and wellbeing.

"Surveys show that people who are properly hydrated feel better and perform better," the spokesperson stated.

"For most people this is typically around two litres of fluid a day and bottled water provides a convenient, healthy and enjoyable way to stay hydrated."

Source: Journal of the American Society of Nephrology (JASN) Published online ahead of print 10.1681/ASN.2008030274 "Just Add Water" Authors: D. Negoianu, S. Goldfarb