With our modern lifestyles thirst is the least reliable of our instincts unless you revert to basics.
A good way to understand your hydration needs is to give up all other drinks other than water for seven days.
If you drink nothing other than water you will get the measure of just how thirsty your body really is.
Be prepared to be surprised.
Experts agree that the average person needs to drink around two litres of water a day, though that assumes they will be consuming another two litres through their food.
Isotonic drinks typically contain around 6 per cent carbohydrates and their purpose is twofold: to provide energy during sport and to replace electrolytes like sodium and potassium after extensive sweating.
Isotonic drinks are thought by sports scientists to be better than water after prolonged activity but they create a calorie burden for people who are not engaged in demanding sports.
Typically they are marketed at the sports enthusiast, active or passive.
Haydn Shaughnessy