Water advice to drink 8 glasses a day a myth
15 July 2011
Litre for litre, bottled water is "more expensive than oil", a Scottish GP says, noting advice to drink more of it was often based on industry spin rather than hard science.
In a BMJ editorial, Dr Margaret McCartney said research underpinning the recommendation that people drink 6-8 glasses of water or fluids per day - as recommended by the National Health Service in the UK - was now "thoroughly debunked nonsense" (BMJ 2011; 343: d4280).
She pointed to a 2008 editorial in the Journal of the American Society of Nephrology that found there was "no clear evidence of benefit from drinking increased amounts of water ... In fact, there is simply a lack of evidence in general" (J Am Soc Nephrol 2008; 19: 1041-43).
Dr McCartney said while there were studies showing that hydration was linked to improved cognition (thinking), and it was protective for kidney function, excessive water intake could increase the risk of upper urinary tract infection or hyponatraemia (low blood sodium level).
There was also the environmental hazard posed by the rising number of discarded plastic bottles. The UK's bottled water industry has reported annual consumption of 33 litres per person, and this figure was rising year-on-year.
"There is still no evidence that we need to drink more than we naturally want, and there may be unintended harms from an enforcement to drink more water," Dr McCartney, of Glasgow, said.
"There are many organisations with vested interests who would like to tell doctors and patients what to do. We should just say no."
Last Reviewed: 15 July 2011
- 1. McCartney M. Waterlogged? BMJ 2011; 343: d4280. [Epub 2011 Jul 12.] doi: 10.1136/bmj.d4280. http://www.bmj.com/content/343/bmj.d4280.extract (accessed Jul 2011).
2. Negoianu D, Goldfarb S. Just add water. J Am Soc Nephrol 2008; 19: 1041-43. [Epub 2008 Apr 2.] doi: 10.1681/ASN.2008030274. http://jasn.asnjournals.org/content/19/6/1041.long (accessed Jul 2011).
