Is it a myth that drinking at least eight glasses of water a day is necessary to prevent dehydration? Dr. Margert McCartney, a GP (general practitioner, primary care physician) says it is more than nonsense "it is debunked nonsense".
There is no available compelling evidence which demonstrates the benefits from drinking lots of water, Dr. McCartney writes in the BMJ (British Medical Journal). However, advocates for the "we don't drink enough water" myth abound - even the National Health Service (NHS) of the UK is an advocate.
On its website, NHS Choices writes:
"Try to drink about six to eight glasses of water (or other fluids) a
day to prevent dehydration."
Several UK schools insist that their kids walk about with a bottle of water.
Dr. McCartney accuses several organizations which have a vested interest in high water consumption of reinforcing this myth.
French food company Danone, which makes and markets Evian and Volvic, tells people to drink from 1.5 to 2 liters of water each day. The company says it is "The simplest and healthiest hydration advice you can give." The company even warns people of the dangers of developing several diseases as a result of mild dehydration.
So, why is there no quality-published proof available to back these claims, McCartney wonders.
McCartney points to a number of studies which, in fact, show that there is no compelling evidence demonstrating the benefits of drinking lots of water. There may even be some unintentional harm associated with excessive rehydration.
"It would seem, therefore, that water is not a simple solution to
multiple health problems."
Several advocates say that children who drink lots of water can concentrate better and have enhanced mental performance. However, these claims have never been confirmed in research studies. Even data claiming to show that drinking lots of water prevents childhood obesity/overweight are not unbiased, the author adds.
Some medical conditions do require increased water consumption - a patient with recurrent kidney stones does.
"In other words, this is a complex situation not easily remedied by telling everyone to drink more."
Even though Danone insists consumers need "informed choices", their own evidence does not support their call to action.
The author concluded:
"There are many organizations with vested interests who would like to tell doctors and patients what to do. We should just say no."
"BMJ 2011; 343:d4280 doi: 10.1136/bmj.d4280
Written by Christian Nordqvist