H2O: life's essential ingredient

PUBLISHED : Sunday, 14 August, 2011, 12:00am
UPDATED : Sunday, 14 August, 2011, 12:00am


Zoe asks: How much water do we need to drink every day?

Wynnie says: Water is essential for life. Healthy humans can survive for 60 days without food, but we can't live for longer than a week without water. Our bodies contain around 10-12 gallons of water, which is needed:

to regulate body temperature

to transport nutrients and oxygen to cells and take waste products and toxins away

to lubricate tissues such as the mouth, eyes, nose

as components for our blood, saliva, stomach acid (for digestion) and urine

to lubricate joints

to help protect organs such as the lungs and heart

On average, we lose about 10 cups of water a day as a result of sweating, urinating, breathing and bowel movements. To prevent dehydration, your body needs a frequent supply of water from drinking liquids. Some foods contain water, too; for example, fruits like watermelon and tomatoes are more than 90 per cent water.

Our bodies are very sensitive to loss of water: a 1 per cent loss of body water will trigger sensations of thirst, 2-5 per cent loss of body water will lead to a dry mouth, tiredness, lightheadedness and headache, and any more than 11 per cent loss could lead to death.

The 2007 Behavioural Risk Factors Survey conducted by Hong Kong's Department of Health shows that nearly a third of adults drink fewer than six cups of fluids daily. This falls short of the recommendation from the Food Standards Agency in the UK, which says people living in moderate climates should drink six to eight glasses of fluids to prevent dehydration.

The Mayo Clinic in the US recommends we drink more during

Increased physical activity

Hot, humid weather

Dry indoor air and high altitudes

An illness, particularly one accompanied by fever, vomiting or diarrhoea

If you're not sure if you're drinking enough fluids, check your urine. A small quantity of dark coloured urine means you're not drinking enough. Drink more so your urine is nearly colourless.

Drinking water is the best way to replace lost fluids, but other beverages such as milk, soy milk, soup and fruit juice are also effective. Tea and coffee have diuretic effects which means they cause your body to lose more water by increasing urination.

Make sure you drink enough:

Drink a glass of water as soon as you wake up.

Carry a bottle of water with you everywhere.

Keep a glass of water at your desk, and take regular sips as you study.

Add flavour to your water with a slice of lime, lemon, cucumber or fresh ginger, or a cut strawberry, fresh coconut or sprig of mint.

Eat ice-cold watermelon slices, frozen lychees or a juicy pear.

Have a fruit smoothie instead of a caffeinated drink.

Start meals with a clear soup.

If you're having fruit juice, dilute it with water.

Zoe's diary

Breakfast: Noodles with fish balls and vegetables

Lunch: Spaghetti with meat sauce/ fried pork ramen/ baked pork chop rice; hot milk tea

Snack: Cheesecake or biscuits

Dinner: Bowl of rice, vegetables, meat dishes, Chinese soup, fruits

Exercise: 30 minutes walking every day, 30 minutes jogging once a week, 50 sets sit-ups every other day

Wynnie Chan is a British-trained nutritionist. If you've got a question for her or would like to be featured in this column, e-mail nutrition@scmp.com