
A suitable allowance of water for adults is 2.5 liters daily in most instances. An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods.
The 2.5 litres was changed to 8 x 8 fluid ounce cups in later recommendations, but is otherwise unchanged.
A couple of things are worth noting about this information (which hasn't really changed in over 60 years). The first is the line 'An ordinary standard for diverse persons is 1 milliliter for each calorie of food'. This seems much more reasonable to me - tying water consumption to caloric intake - than simply drinking 2.5 litres of water. It would seem sensible that an athlete consuming 4,000 kCals per day would require a greater water consumption than one getting through 1,500 (for health reasons - we're not talking about preparing for bodybuilding competions here).
The second is the part of the guideline which seems to have been overlooked in later versions - 'Most of this quantity is contained in prepared foods'. I wonder just how much diets have changed in 60 years.
Further observations - there appears to be a strong emphasis these days on 'pure' water consumption. Whilst I always make sure to drink a glass or two of water when also consuming alcohol, coffee or high-protein foods; the bulk of my non-food water consumption comes from green tea. This doesn't appear - at least in my case - to make any difference whatsoever.
i Valtin H. "Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8x8"? Am J Physiol Regul Integr Comp Physiol 2002;283:R993-R1004