Advice to drink 8 glasses a day doesn’t hold water

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 NHS in the UK – was now “thoroughly debunked nonsense”.

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.”

Dr McCartney said while there were studies showing that hydration was linked to improved cognition, and it was protective for kidney function, excessive water intake could increase the risk of upper urinary tract infection or hyponatraemia.

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