The idea that drinking eight glasses of water a day is good for your health has been dismissed as a myth.
Scientists say there is no evidence drinking large amounts of water is beneficial for the average healthy person, and do not even know how this widely held belief came about.
Specialists in kidney conditions in America reviewed research on claims eight 8oz glasses of water help flush toxins from the body, preventing weight gain and improving skin tone.
Dr Dan Negoianu and Dr Stanley Goldfarb, of the Renal, Electrolyte and Hypertension Division at the University of Pennsylvania, said no single study indicated average healthy people needed to drink this amount of water - a total of 3.3 pints - each day.
“Indeed, it is unclear where this recommendation came from,” they say in a review in the Journal of the American Society of Nephrology.
The researchers did find some evidence that individuals in hot, dry climates, as well as athletes, need to increase the amount of water they drink. Studies have also shown that drinking lots of water helps the body to clear salt and urea.
But no studies have found any benefit to the organs of increased water intake.
Drs Negoianu and Goldfarb also investigated the theory that drinking more water makes you feel full and curbs appetite.
Proponents say this may help maintain a healthy weight and fight obesity, but the evidence for this claim remains inconclusive, states the review.
No carefully designed clinical trials have measured the effects of water intake on weight maintenance.
Headaches also are often attributed to water deprivation, but there is little data to back this up, claim the scientists.
Only one small trial has addressed this question, and while trial participants who increased their water intake experienced fewer headaches than those who did not, the results were not statistically significant.
In addition, water has been touted as an elixir for improved skin tone.
The authors said that while dehydration can decrease skin stiffness, no studies have shown any clinical benefit to skin tone as a result of increased water intake.
The literature review by Drs Negoianu and Goldfarb reveals there is no clear evidence of benefit from increasing water intake. On the other hand, no clear evidence exists of a lack of benefit. “There is simply a lack of evidence in general,” they explain.
On average, the body uses between 1.7 and 2.6 pints (one-1.5 litres) of water daily and more in high temperatures or when exercising.
This is replaced through drinks but a large amount is also contained in food, so it is not necessary to drink an equivalent amount to replace water levels.
Too much water can affect the balance of salts in the body causing “water intoxication”, which can be fatal.