Myths busted: How much water do we really need

Water. We know we should drink lots, but how much, how cold and in what form?

Eight glasses a day?

Actually, recommendations for six, eight or 10 glasses exist, depending on which authority you go to. In 2006, the National Health & Medical Research Council in Australia revised its recommended nutrition intakes and upped our fluid requirements to 2.8 litres for women, and 3.4 litres for males, more in hot humid weather or if you’re very active.

But bear in mind these figures are for total fluid – not just water – and include the water you get from food. Fruit, for instance, contains anywhere from 60–95 per cent water; even a dry food like bread has some 40 per cent. So for most people, that means you need only about five to six glasses of actual fluid, not the full eight or 10 suggested.

Does coffee count?

Another myth is caffeinated drinks don’t count toward your eight-a-day – also not true. Coffee, energy drinks, cola and tea do have some diuretic effect but you have to consume loads before this kicks in.

You can’t have too much, right?

Actually, wrong. It sounds odd, considering around 60 per cent of our body is composed of water, but you can overdo it – it’s called water overload, or hyponatraemia. When the body takes in too much water, the salt levels in the blood are diluted. As a result, the body’s cells swell, which can lead to epileptic fits and brain damage. In 2007, a Californian woman died after taking part in a water drinking contest. In 2008, a UK woman suffered permanent brain damage after going on a detox diet to lose weight where she consumed four litres a day of water.

Adverse effects are also often reported in marathon runners who drink too much before an event. If you’re concerned about this, swap water for a sports drink with electrolytes – especially sodium.

Does drinking icy water affect metabolic rate?

This is a myth that’s been doing the rounds of gyms. It goes like this: if water entering your system is much colder (say, less than 4ºC) than your body temperature (usually around 37°C), your body has to work hard to counteract the drop in internal temperature – so you draw from your fat stores for extra fuel. But in reality, only a few kilojoules are needed to keep your body temperature even.

Bottom line

Water is the ideal drink – it’s cheap, has no kilojoules or caffeine, and keeps you hydrated. As with everything in nutrition however, consume it in moderation.