How much water should really be drunk daily for optimal health?

This depends on a number of factors, one being how much fluid you are losing in the day. If you go for a run on a hot, humid day, you’ll lose a lot more fluid than playing PlayStation at home. This fluid loss needs to be replaced. So it depends on the ambient temperature or climate and level of activity, but you also lose water through your breath, sweat, urine and bowel. Aim to drink about two to three litres per day. A good rule of thumb: drink enough so you rarely feel thirsty and produce approximately 1.5 litres or more of colourless or palecoloured urine per day.