Monday, 18 January 2010

How Much Water Is Enough?

Paying heed to the amount of fluids that we drink daily may be more important than you think.

While eight glasses water per day is a reliable guide, factors such as gender, level of activity, diet and body weight influence the exact amount of water that one needs.

“An individual’s daily water intake can vary widely,” said Dr Chin Khong Ling, a family physician at Healthway Medical Sengkang Clinic.

“Generally, adult females need 2.2 litres while males need 2.9 litres of water daily, but this can go up to 4.5 litres for those doing manual work in high temperatures,” he added.

This is because exertion causes the body to lose water through sweat. Other than perspiration, water is also lost through breathing, urine and stools, said Dr Wong Wei Mon, s senior physician at Raffles Medical.

Even mild dehydration, which refers to a fluid deficit of 2 per cent, can wreak havoc on one’s body and mind.

“Physically, one may experience perceived or real muscle weakness,” said general practitioner Karen Soh of Pacific Wellness Centre. “Psychological effects include tiredness, headaches and a reduced ability to concentrate and analyse information,” she said.

Research such as a 1998 study published in the European Journal Of Clinical Nutrition found that mild dehydration decreases mathematical ability, visual-motor function and short-term memory. Later studies also found adverse effects on perception and reaction time.

The reason for such serious consequences is water’s key role in major bodily functions.

“Water makes up more than 70 per cent of most tissues, including muscle, skin and visceral organs.” Said Dr Wong. “Our bodies need water for blood circulation, digestion, to maintain body temperature and for hormonal communication between the organs.”

All three doctors agreed that thirst is a poor indicator of dehydration.

“By the time you get thirst, it is too late,” said Dr Wong adding that we should drink water frequently throughout the day and avoid too many diuretic beverages like coffee and alcohol, which promote water loss through urination.

However, one should not overdo drinking either. Too much water leads to water intoxication, where electrolyte levels in the blood stream are diluted to very low levels, warned Dr Soh.

“Water intoxication can occur in endurance athletes who drink plain water without replacing the electrolytes lost through sweat or in those involved in low-intensity exercise but who over-hydrate in the belief that tremendous water intake is beneficial,” she said.

Dr Soh added that such cases are rare as the kidneys will try to remove the excess fluid, and one should consider electrolyte-containing beverages after physical exertion instead of plain bottled or tap water.

- Poon Chian Hui 

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