Everyone knows that a lack of water is fatal; it makes up 60 per cent of your body weight after all, and every bodily system depends on it. A person can survive a maximum of just three days without water - or two in a climate like Abu Dhabi's, even if you are in the shade - whereas you can survive four to six weeks without food in certain conditions. But is it possible to drink too much water? The answer is yes, and with dangerous consequences.
Dawn Page, 52, from Oxfordshire in the UK, was recently awarded Dh5,480,000 (£800,000) in damages after she was left brain damaged by a detoxification plan called The Amazing Hydration Diet. In 2001, she was advised by a nutritional therapist to follow the plan, which involved drinking two litres of mineral water per day as well the tea and other fluids that she normally drank, while drastically reducing her salt intake.
The mother of two, who weighed 76 kg, started vomiting after a few days and was urged to increase her water intake to 2.8 litres a day and cut her salt intake further. She later had an epileptic seizure, which damaged her memory, speech and concentration. Doctors diagnosed low salt levels in her body, known as hyponatremia, or water intoxication. Last year, a Californian woman died after taking part in a water-drinking contest. Jennifer Strange, 28, had taken part in a "Hold Your Wee for a Wii" game for a radio station, which promised the winner a Nintendo Wii. Contestants were first given 225-millilitre bottles to drink without going to the toilet. After eight rounds, contestants drank 0.5 litre bottles. Strange may have drunk nearly 7.5 litres, witnesses said. Local assistant coroner Ed Smith said initial tests showed death was "consistent with water intoxication".
And in 2003, a 22-year-old man died after completing his first London Marathon because he drank too much water. David Rogers, who finished the race in 3hours 30 minutes, collapsed and died in Charing Cross Hospital. The fitness instructor from Milton Keynes died from hyponatremia. So even the most natural, life-giving substance on the planet can be a killer in excess. Experts say drinking too much water can eventually cause your brain to swell, preventing it from regulating your breathing and causing death. Initial symptoms of over-hydration include dizziness, nausea and confusion.
How does it happen? Most of the water that enters the body leaves it in the form of urine or sweat. The amount of water in the body is regulated to control the level of elements like salt in the blood. If you drink too much water, your kidneys cannot get rid of it fast enough, the concentrations of salt fall and your blood becomes more diluted. The professor Robert Forrest, a retired consultant in clinical chemistry and forensic toxicology at the Royal Hallamshire Hospital in Sheffield, explains that over time, the extra water fills various organs, causing them to swell. This swelling is especially dangerous to your brain because it's confined by your skull.
"When the brain swells, it is inside a bony box so has nowhere to go," he says. "The pressure increases in the skull and you may get a headache. As the brain is squeezed it compresses vital regions regulating functions such as breathing." Marathon runners have long been aware of the risks, as competitors who drank too much water collapsed during races. Research found that runners were "stocking up" on water before the marathon to avoid dehydration, and assuming they would sweat out the excess during the race.
Wrong. The problem during a marathon is not so much one of high water levels but low sodium levels. The heat generated by the body during exercise makes the runner sweat, but sweat contains high levels of salt which is not replaced by drinking water before, or even during, the race. So all marathons now offer sport drinks that contain salts and minerals to replace the sodium that is sweated out during the event.
But there is so much misinformation about water intake that the average person - not on a faddy diet or entering a marathon - can feel justifiably confused. Experts say that is because while the question "How much water should I be drinking?" is a simple one, there are no pat answers. Your water needs depend on many things, including your health, how active you are and where you live. The so-called "8x8 rule" - drinking eight eight-ounce (225-millilitre) glasses of fluid a day - is one approach. This equates to about 1.9 litres in total.
Alternatively, experts say, knowing more about your body's need for fluids helps you estimate more accurately how much water to drink each day. The average urine output for adults is about 1.5 litres (6.3 cups) a day. You lose nearly an additional litre of water a day through breathing, sweating and bowel movements. The British Dietetic Association advises that the average adult should consume 2.5 litres of water per day. Of this, 1.8 litres - the equivalent of six to seven glasses of water per day - must be obtained directly from beverages. This should be increased during hot weather or during and after periods of physical activity.
But drinking several litres over a relatively short period of time could be enough to cause water intoxication. A spokesman for the BDA said: "If you are going to the toilet more than once every two hours or so that might be too much, especially if your urine is clear." But, he added, drinking too much water was "unusual". Water is the major ingredient of all drinks: carbonated and still drinks are 65 per cent water, diluted squashes are 86 per cent water (after dilution) and fruit juices are 90 per cent water. It is a myth is that caffeinated drinks don't count toward your water intake. Coffee, tea and coke do have some diuretic effect, making you want to urinate more often, but experts say you can still count them as about half to two-thirds their actual volume.
Drinking plain water, which is calorie free, is still however the most effective way of replacing lost fluids. If you exercise or engage in any activity that makes you sweat, you need to drink extra water. You also need to drink additional water in hot or humid weather to help lower your body temperature and to replace what you lose through sweating. In the Middle East, you should aim to drink fluids regularly throughout the day rather than just when you are thirsty. If you are worried whether you are getting enough, one simple test is to check the colour of your urine. The paler and more straw-coloured, the better.
Most people will come to no harm if they stick to drinking two to three litres of fluid per day. But children should drink approximately half this amount, depending on their age. A baby can get water intoxication as a result of drinking several bottles of water a day or from drinking infant formula that has been diluted too much. Incidentally, food provides about 20 per cent of total water intake, while the remaining 80 per cent comes from water and beverages of all kinds. For example, many fruits and vegetables, such as watermelon and tomatoes, are mostly water. The bottom line, say experts, is this: it's possible to drink too much water, but unless you are running a marathon or are an infant, water intoxication is a rare condition.
