At the recent Osim Triathlon, eventual Elite men's champion Anthony McSweeney, 21, collapsed at the end of his race due to a condition common among athletes - dehydration.

Even if you are not a professional athlete, the importance of adequate hydration every day cannot be overstated.

Endocrinologist Stanley Liew of Raffles Hospital says: "Water performs many vital functions in the body, such as transportation of nutrients, elimination of waste products and temperature regulation."

How much water should a person drink before it is considered enough?

Dr Liew and his colleague, traditional Chinese medicine (TCM) physician Zhao Xu Hong, agree on one point: Athletes such as long-distance runners do not need to drink too much before a race. Instead, they should refuel along the way.

From the Western medical science perspective, Dr Liew says the oft-prescribed eight glasses of water a day is nothing more than a guide.

"It is not a minimum requirement to stay healthy. On average, water intake of 1.5 litres or six glasses a day is adequate," he says, adding that the human body's thirst mechanism is generally reliable, except during illness or in extreme environments such as deserts.

It may even be dangerous to drink too much water within a short period of time. Water intoxication can result from drinking more than 1.5 litres of water within an hour.

Dr Liew also recommends that during an endurance sporting event, you should drink just enough to be sure you lose no more than 2 per cent of your pre-exercise weight.

In practice, it is impossible for athletes to be so precise, especially during a competition.

Recruitment consultant Jan Cheang, 44, who runs an average of three races a year, including a marathon, drinks up to 2 litres of water a day, two days before a race.

"During the race, I force myself to have a sip at each drinking station even if I do not feel thirsty. I also alternate between water and isotonic drinks," she says.

This is similar advice that TCM practitioners such as Ms Zhao gives everyone, athlete or not, to hydrate himself - drink small amounts of water regularly throughout the day.

She adds that those with different physical constitutions have different needs, with the environment, weather and diet also playing a part.

For example, if a person has too much "yang" energy and too little "yin" energy, he has to drink more water to reduce the internal "heat".

In addition, Ms Zhao says such a person can consume ice-cold drinks without adverse effects, even though drinking warm or room temperature water is generally recommended.

On the flip side, a lack of "yang" energy and an excess of "yin" energy in a person means he should drink less water due to a lower metabolic rate.

People who are heavier also tend to have a lower metabolic rate. "We would discourage them from drinking too much water since the rate of digestion is thus slower," says Ms Zhao.

According to TCM belief, the timing of one's water intake is also important. It is advisable to drink a glass of water first thing every morning as this will "awaken" the digestive system and, in turn, regulate bowel movements and improve the circulatory system, which can include lymphatic functions, in the human body.

Drinking too much water before bedtime may disrupt sleep as you may need to wake up to go to the washroom.

Ms Zhao notes: "When we are sleeping, our body is at rest and thus the required water intake at this state is lower."

She adds that it is best to avoid drinking too much water before and after meals as this will disrupt the rate of absorption of nutrients and digestion.

nicy@sph.com.sg

This article was first published in The Straits Times.