'˜Drinking plenty of water' may be old wives' tale

The advice to drink plenty of fluids when unwell lacks evidence, experts say.

Doctors at King’s College Hospital in London questioned the recommendation after treating a 59-year-old woman who had drunk so much water that she became gravely ill.

The woman effectively overdosed on water after developing symptoms of a urinary tract infection, something she had suffered from before.

She recalled being told by a doctor previously to drink lots of water - half a pint every 30 minutes - though she said she thought in this case, she had consumed more to “flush out her system”.

The woman was admitted to A&E, where doctors found she was suffering from acute hyponatraemia, which is caused by low salt levels in the blood.

Writing in the journal BMJ Case Reports, doctors described how the woman got worse, explaining: “During her visit to the emergency department, she became progressively shaky and muddled. She vomited several times, was tremulous and exhibited significant speech difficulties.”

Although doctors were able to save the woman’s life with treatment including restricting her fluid intake to a litre over the next 24 hours, they described another case in which a young woman suffering from gastroenteritis died after consuming too much water.

Dr Imran Rafi, chairman of clinical innovation and research at the Royal College of GPs, said: “There is no steadfast recommendation as to how much water people should drink in order to stay healthy, but the key thing is to keep hydrated.”