Should you drink only when thirsty, or before thirst strikes?

Water is the cornerstone of human biology. According to the Encyclopaedia Britannica, we are each about 60 per cent water by weight. Opinion differs about when our bodily reservoir needs replenishing. Some sources advise only drinking when thirsty, in step with nature. Others champion frequent hydration ahead of thirst.

Acupuncturist and general practitioner Liem Quang Le, who has worked with Olympic athletes, advocates the second, anticipatory approach. "Always make sure you drink before you are thirsty - you are already dehydrated when your body sends a signal to your brain that you should drink water," Le says and proposes you consume one litre for every 23kg of body weight daily.

During exercise, drink water roughly every 20 minutes, he says. Also drink between meals. Then, according to Le, you avoid diluting your stomach acids, so nutrients are readily absorbed.

Le says your body counts on being hydrated to lubricate your internal organs. Besides, hydration keeps your skin looking supple and healthy. It also regulates your body temperature, aids weight control, boosts energy and flushes out waste and toxins, helping maintain your immune system. So hydrate fully and your body will love you for it.

Even mild dehydration, which is defined as about 1.5 per cent loss of normal water volume in the body, can alter a person's mood, energy level and ability to think clearly, according to two studies conducted at the University of Connecticut's human performance laboratory.

The tests showed that it didn't matter if a person had just walked for 40 minutes on a treadmill or was sitting at rest - the adverse effects of mild dehydration were the same.