Drink eight glasses of water a day

Many people believe that the source of this myth was a 1945 recommendation by the American Food and Nutrition Board that said people need about 2.5 litres of water a day. But they ignored the sentence that followed closely behind. It read: “Most of this quantity is contained in prepared foods.”

Water is present in fruit and vegetables. It’s in juice, it’s in beer, it’s in tea and coffee.

A 2007 paper in the BMJ on medical myths by Rachel C Vreeman and Aaron E Carroll said there was a “complete lack of evidence supporting the recommendation to drink six to eight glasses of water a day”. It also highlighted that drinking excess amounts of water can be dangerous, resulting in water intoxication, hyponatraemia, and even death.