Water health myths

Water is amazing - we can't live without it and we are, in fact, mostly composed of it. So it is not surprising that a whole bunch of half-truths and myths exist about water, especially when it comes to your health.

So here are our top five myths about water.

Myth 1: We should drink eight glasses of water a day to avoid dehydration

Probably one of the most widely-believed yet false beliefs about water - no doubt encouraged by bottled water brands.

According to the British Dietetic Association and the NHS, we should try consume the equivalent of around six to eight glasses of fluid a day, but that's fluid, not water.

Much of this can be obtained from the food we eat - fruit and vegetables are 80-90 per cent water by weight - and other drinks including milk, tea and coffee.

But even this has come under criticism. Scottish GP Dr Margaret McCartney wrote in the British Medical Journal that there was no strong evidence for the current advice, adding that it was "not only nonsense, but thoroughly debunked nonsense."

Obviously in hotter, sweatier conditions we need to up our intake to make up for the extra loss, but again, any non-alcoholic drink will suffice.

Your body is very good at regulating water levels; it will get rid of excess by sweat and urine and when levels are low you will feel thirsty and compelled to drink.

Myth 2: Coffee, tea and other beverages "dehydrate" you

While it is true that caffeine has a diuretic effect (it makes you want to pee), this is very mild compared with the amount of water contained in the drink. These drinks mostly contribute to your body's need for water, without the risk of dehydration.

Myth 3: Water is harmless

Generally speaking, water is non-toxic. But you can drink too much water. In extreme cases drinking too much water can cause an electrolyte imbalance in the body, known as "water intoxication."

Athletes in extreme sports, such as marathon runners, have been known to suffer from this condition. Their sport causes them to sweat profusely, leading to a loss of both water and electrolytes, including sodium. But if they drink a lot of water in a short period of time without replacing the lost electrolytes, sodium levels in the blood fall, which can be potentially life-threatening.

Myth 4: Bottled water is safer than tap water

Would you drink a liquid that may have been exposed to pesticides, man-made fertilisers and even radioactive materials, and destroys the environment? Then you will probably be happy to pay 1,500 times the going rate to drink water from a plastic bottle.

Tap water is subject to stringent health and safety requirements. It is continuously tested and safe to drink. Bottled waters often come from exactly the same sources as tap water - in fact some are tap water.

Much bottled water is prepared with lower safety standards than tap water, and it consumes vast resources to bottle, ship, market and sell it. That's why it costs around 1,500 times more per drink than tap water, which is safe, cheap, convenient and by the far the most eco-friendly way to get water.

Myth 5: Water can help you lose weight

There is some truth is this idea, but only some.

Going back to myth 1, drinking calorie-free and sugar-free water is a better way to get your daily fluid intake than gulping sugary, high-calorie soft drinks.

Some studies have also shown that drinking water before a meal can help you eat less.

But the key point here is that you do in fact need to eat less, and reduce your calorie intake; the water itself, does not in any way reduce your body fat.