Lack of response from NHS on their advice to drink 1.2 litres of water a day.

I read a claim on the on the NHS Choices website saying ‘research measuring water loss has shown that we should drink about 1.2 litres of fluid every day to stop us getting dehydrated.’ This is similar to the common idea of drinking 7 cups of water a day, but where does this exact volume come from? I asked for the evidence behind this claim.

I got a short response from the NHS Choices Editorial Team. They said that the information on their website is ‘consistent with current advice from the Department of Health. This advice is based on evidence from Fitzsimmons J.T. "The Physiology of Thirst and Sodium Appetite" (1979).’ After sifting through the almost 600 page book I was unable to find the specific study investigating human water loss and dehydration. In my opinion, publications from 1979 should not always be considered ‘current’, and therefore I am not satisfied with the evidence supplied.