Can you drink too much water? Experts say yes

By Dr. Ananya Mandal, MDJul 13 2011

Drinking adequate amounts of water is said to prevent kidney damage, help lose weight and increase concentration. However experts now warn that drinking eight glasses of water a day is not good after all – and could be harmful. They say that scientific claims behind long-standing government guidelines are worse than ‘nonsense’. The NHS – along with leading doctors and nutritionists – advises the public to drink about 1.2 litres (or two-and-a-half pints) of water per day.

According to a new report the dangers of dehydration is a myth and there is no evidence behind claims that water prevents multiple health problems. Glasgow-based GP Margaret McCartney says the NHS Choices website’s advice that people should drink six to eight glasses a day is ‘not only nonsense, but thoroughly debunked nonsense’. She adds that the benefits of the drink are often exaggerated by ‘organizations with vested interests’ such as bottled water brands.

Dr McCartney wrote in the British Medical Journal that research shows drinking when not thirsty can impair concentration, rather than boost it, and separate evidence suggests that chemicals used for disinfection found in bottled water could be bad for health. Drinking excessive amounts can also lead to loss of sleep as people have to get up in the night to go to the toilet, and other studies show it can even cause kidney damage, instead of preventing it. Dr McCartney also warns that taking on too much water can lead to a rare but potentially fatal condition called hyponatraemia, which sees the body’s salt levels drop and can lead to swelling of the brain.

Professor Stanley Goldfarb, a metabolism expert from the University of Pennsylvania in the U.S., says: “The current evidence is that there really is no evidence. ‘If children drank more water rather than getting extra calories from soda, that’s good… [but] there is no evidence that drinking water before meals reduces appetite during a meal.”

About 2.06 billion litres of bottled water were drunk in Britain last year, compared with 1.42 billion litres in 2000. ‘Hydration for Health’, an initiative aimed at medics to promote the drinking of water, which was created and is sponsored by Danone, the French maker of Evian, Volvic and Badoit bottled waters, says “many people, including children, are not drinking enough”. It recommends “1.5 to 2 litres of water daily is the simplest and healthiest hydration advice you can give.”

Consultant nutritionist Jane Griffin, said, “Up-to-date information from the European Food Safety Authority is that men should get 2.5 litres and women two litres of fluids each day. But that includes the fluid you get from food. Most foods contain some water. If you get your five portions of fruit and vegetables a day - that makes a significant contribution.”