MYTH: Everyone needs to drink eight glasses of water a day
THE TRUTH: There is no truth to the claim that everyone needs exactly eight cups of water a day. Water is important for good health and it is your best choice to satisfy thirst, but other liquids are also hydrating. The amount of water you need to hydrate your body varies daily and depends on factors like your gender, physical size and how active you are, as well as environmental factors like heat and humidity. To help stay hydrated, drink plain water (tap or bottled) plus other beverages like milk, coffee or tea throughout the day. And remember to drink more in hot weather and when you are very active.
Source: Dietitians of Canada