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Last Updated: Apr 16, 2008 - 5:52:06 PM |
THURSDAY April 3, 2008 (Foodconsumer.org) -- A recent review study suggests there is no reason for a healthy person to drink as much as eight glasses of eight ounces of drinking water a day. That much water may not do any good or harm either.
The study published in the June 2008 issue of the Journal of the American Society of Nephrology (JASN) showed little evidence to validate claims on the benefits of drinking water in large quantity including clearing toxins, warding off weight gain by suppressing appetite and improving skin tone among others.
Dan Negoianu, MD, and Stanley Goldfarb, MD, of the Renal, Electrolyte, and Hypertension Division at the University of Pennsylvania in Philadelphia, PA reviewed previous clinical studies on drinking water.
Individuals in hot, dry climates, as well as athletes, have an increased need for water and people with certain diseases benefit from increased fluid intake, the researchers found.
But data are lacking for average and health individuals and no single study provides evidence that supports the recommendation of drinking eight glasses of water each day. It's not clear where the recommendation came from, according to the researchers.
The review found drinking water has an impact on clearance of various substances such as sodium and urea by the kidney. But it's unclear what sort of clinical benefit may be provided. This means the claim that increased water intake improves kidney function and helps to clear toxins has not been substantiated.
The study also found no evidence to suggest drinking eight glasses of water a day would provide benefits to organs, help people maintain their weight or even help fight obesity.
Drs. Negoianu and Goldfarb did find in a small trial people having increased water intake experienced fewer episodes of headaches than those who did not, but they said the results were not statistically significant.
With regard to the skin tone, no studies have shown increased intake of water rendered any clinical benefit to skin tone although dehydration can decrease skin turgor, the study said.
The researchers said essentially there is no evidence to suggest drinking eight glasses of water per day does or does not provide benefits.
"There is simply a lack of evidence in general," they explained.
A scientist affiliated with foodconsumer.org suggested that people should not be discouraged by the study from drinking enough water a day, particularly along with meals.
But he cautioned that people should drink healthy water only. Ideal water to drink is the one that is free of pollutants, slightly alkaline and with lots of essential minerals.
Editor’s note: To help readers understand that water is a vital nutrient and humans can’t survive without sufficient water, we publish below a fact sheet.
Water as a nutrient: what you need to know
1) The human body is made up of 55 to 75 percent water, which is the basis of blood, digestive juices, urine and perspiration;
2) Water is continuously lost every second from the lungs, skin, urine and feces. The amount of water we need each day depends upon the body metabolism, the weather, the food we eat and physical activity;
3) Men have more water in their bodies than women. Adults lose about 2.5-3 liters of water per day. Hot weather, exercise, and air travel increase loss of water;
4) Food provides one third of water we need and the rest needs provided by drinks including drinking water;
5) Water in the body helps maintain the health and integrity of cells; keep the blood flow freely through blood vessels; eliminate the by-products of the body's metabolism, excess electrolytes and urea; regulate body temperature; keep mucous membranes moist; lubricate and cushion joints; reduce risk of cystitis; help digestion and prevent constipation; improve skin texture and appearance; and mediate transportation of nutrients and oxygen to cells;
6) Loss of too water causes dehydration which results in symptoms including increased headaches, lethargy, mood changes and slow responses, dry nasal passages, dry or cracked lips, dark-colored urine, weakness, tiredness, confusion and hallucinations;
7) Dehydration can be caused by increased sweating, not drinking enough water, increased urination, diarrhea or vomiting and recovering from burns;
8) More water is needed in people who are eating a high protein diet or a high fiber diet; children; patients having diarrhea or vomiting; and those who are physically active or exposed to warm or hot weather;
9) Drinking too much water (many liters a day) may cause a condition known as water intoxication or hyponatremia. This happens when sodium in the blood drops to a dangerously low level. The condition causes headaches, blurred vision, cramps, swelling of the brain, coma and possibly death;
10) It is generally recommended that 6 to 8 glasses of a variety of fluids can be consumed each day. Some people may need more water if they are physically active, children, people in hot or humid environments, or breastfeeding.
© 2004-2008 by foodconsumer.org unless otherwise specified
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