We are constantly being bombarded with health advice, but not all of it is based on rigorous evidence. New Scientist debunks six common myths Drink eight glasses of water a day.
It's the myth that just won't go away. Almost everyone thinks they don't drink enough water, but the idea that we all should drink lots of it – eight glasses per day – is based on no scientific data whatsoever.
No one really knows where the eight-glasses idea comes from. Some blame the bottled water industry but plenty of doctors and health organisations have also promoted it over the decades. The source might be a 1945 recommendation by the US National Research Council (NRC) that adults should consume 1 millilitre of water for each calorie of food, which adds up to about 2.5 litres per day for men and 2 litres for women.