There is little evidence that drinking loads of water, a recommended 8 glasses of 8 ounces (8x8) per day, improves your health, say scientists from the University of Pennsylvania. The two kidney experts explained that unless you are an athlete or live in a hot place, drinking extra water may be a waste of time.

You can read about this study in the Journal of the American Society of Nephrology, April 2nd online issue. The Editorial will be published in the journal's June, 2008 issue.

It has been claimed that consuming lots of water clears toxins, keeps organs in best condition, improves skin tone and prevents you from putting on weight. The researchers say the evidence to support these claims is very far from compelling.

The researchers explain that we all know what effect dehydration can have on us - as humans, we cannot survive more than several days without water. However, very little research has been carried out on what affect drinking extra water (fluids) may have on human health.

Dan Negoianu, MD, and Stanley Goldfarb, MD, of the Renal, Electrolyte, and Hypertension Division at the University of Pennsylvania, in Philadelphia, PA, decided to find out what the true benefits of drinking additional water might be and examined published clinical studies on the topic.

They found that people who live in hot, dry climates, as well as athletes, need more water than other people. They also found that patients who suffer from specific diseases also do well when their fluid intake is increased. However, they found no solid evidence that showed any health benefits for healthy people who were not athletes and did not live in hot and/or dry climates. Not one study they reviewed indicated that people required an '8x8' intake of water each day.

In their report the authors do not say where this '8x8' recommendation came from. In an interview with Reuters Health Dr. Goldfarb indicated that this 'myth' may have come from the alternative/complementary medicine world.

Kidney function and clearing toxins

The researchers included literature related to the notion that increased water intake improves kidney function and helps to clear toxins in their study. Although the studies indicated that drinking water may have an impact on the clearance of various substances by the kidney, such as sodium and urea, they did not indicate any sort of clinical benefit that might result.

Improving the function of organs

The scientists reviewed studies that tested the effect water might have on the functioning of organs. The studies indicated that water retention varies and often depends on how quickly the water is consumed - if it is gulped down quickly it will most likely be excreted more quickly, while if it is consumed gradually and slowly the body will retain more of it. Nevertheless, none of the studies indicated any benefit to organs as a result of raised water consumption, no matter how quickly it is consumed.

Suppressing appetite, maintaining bodyweight, fighting obesity

They also examined the theory that consuming more water may make a person feel fuller, leading to a smaller appetite for food. Some people claim this is an effective way of preventing weight gain, or fighting obesity. The evidence was not there to back this - the studies remained inconclusive. No carefully designed clinical trials have measured the effects of water intake on weight management, they wrote.

Headaches

There was no data to back up the theory that water deprivation is a reason for headaches. Just one small trial found that some of those who consumed more water reported having fewer headaches; the results were not statistically significant.

Skin Tone

Although studies have shown that dehydration can decrease skin turgor, not one study demonstrated any clinical benefit to skin tone as a result of consuming extra water.

Drs. Negoianu and Goldfarb concluded that there is no clear evidence to indicate that consuming extra water is good for the health - they also stressed that there is no clear evidence of a lack of benefit. "There is simply a lack of evidence in general," they wrote.

"Just Add Water"
Dan Negoianu and Stanley Goldfarb
J. Am. Soc. Nephrol., first published on April 2, 2008 as doi
doi:10.1681/ASN.2008030274
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