Is being dehydrated really as bad for you as being drunk?

YOU’VE heard of drunk drivers, now there’s another peril on the road: the dry driver.

A new study says getting behind t he wheel when dehydrated makes you just as hazardous as being under the influence of alcohol.

The research f rom Loughborough University showed drivers who drank 25 ml (a couple of sips) of water an hour, instead of the recommended 200 ml (a third of a pint), made twice the number of mistakes as those who were well-hydrated.

So how important is water? And should you have it hot or cold? Still or sparkling? Tap or bottled? Here are the answers . . .

DO WE DRINK ENOUGH?

MEDICS say that on the whole we’re a pretty parched lot.

in march, a study warned that the number of people taken to A&E with painful kidney stones has soared. According to Professor Tom Sanders, of King’s college London, dehydration is said to be the most likely cause.

Kidney stones f orm when calcium deposits in urine clump to form crystals in the kidneys and then get trapped in the urethra. When a person is dehydrated, the concentration of deposits is higher.

Emergency admissions for the problem have more than doubled, from 5,063 cases in 2003-2004 to 11,937 in 2013-2014.

SO HOW MUCH SHOULD WE DRINK?

THE European Food Safety Authority recommends that women should drink 1.6 litres (eight glasses) of fluid per day, men two litres (ten glasses) and toddlers 1.3 litres (6½ glasses).

We need water because we are water — it makes up 78 per cent of our brains and two-thirds of the weight of our body.

Water is the vehicle transporting carbohydrates, proteins and vitamins, which are vital to keeping our organs alive. No less important is water’s job of transporting waste materials out of our bodies.

Babies have the highest water content: at birth it’s 78 per cent, dropping to around 65 per cent by their first birthday. So a comparatively small drop in consumption makes a big difference to their little bodies.

The bodies of adult men are 60 per cent water and women about 55 per cent. in women, fat makes up more of the body than men and this does not contain as much water as lean tissue.

WHEN AM I DEHYDRATED?

MILD dehydration sets in when we lose between just 1 or 2 per cent of our body’s normal water volume. For an 11st man, whose body contains 42 litres of water, that’s 840 ml — just four glasses.

But even at this mild point, people start to become confused, says research in 2010 by Tufts University, Boston. Focus and short-term memory start to go.

Even more dangerously, our ability to assess accurately how we feel starts to fade, according to research by Barcelona University psychiatrists last year. This can mean we lose touch with the warning signs from our body that we are beginning to get more seriously dehydrated.

Though rectified quickly after a few glasses of water, frequent mild dehydration can cause longer-term problems, such as tooth decay, as we lack sufficient water to make protective saliva.

Water also helps to cushion joints, staving off arthritis.

HOW IT AFFECTS YOUR BRAIN

THE study on drivers reinforces earlier research by the University of Nebraska’s Human Nutrition centre, which reported that dehydrated young men found it harder to think, remember or coordinate their limbs.

And a brain scan study by psychiatrists at King’s college, London in 2010 found 90 minutes of steady sweating can shrink the brain as much as a year of ageing.

Physical changes caused by dehydration were likened to those in Alzheimer’s patients. if left untreated, severe dehydration can cause seizures, brain damage and death.

TELL-TALE SIGNS

PERHAPS most obviously, one of the first signs of dehydration is feeling thirsty. Other common signs include de headaches, lethargy and feeling lightheaded.

Frequency of urination is another indicator. ator. Healthy i ndividuals should d be able to pass water at least four times a day.

But the best way to tell is by monitoring oring the colour of your urine. Pale yellow is best, while any darker means that the urine i s more concentrated, suggesting you are not drinking enough.

GLUG OR SIP?

ACTRESS Glynis Barber said last week she glugs water straight down i n one glass. The 59- year- old dempsey And makepeace star attributes her youthful bloom to this because ‘research shows that drinking little and often doesn’t help cells replenish properly’.

But there is no reputable cl i ni c al evi dence to support this. What is i mportant is the amount of water you consume each day.

TAP OR BOTTLE?

EXPENSIVE bottled water has the same hydrating abilities as tap water, says the British dietetic Association. A glass straight from the tap is perfect for quenching thirst.

SPARKLING vs STILL

CARBONATED water is usually just as hydrating as plain tapwater.

There are fears that carbonated water may deplete people’s levels of calcium and thin their bones, as do fizzy drinks, but there is no clinical evidence.

it’s the other ingredients in fizzy soft drinks, such as sugars, colourants and preservatives, that nutritionists say could be to blame.

But bubbles do cause wind and may make people feel bloated.

And some carbonated mineral waters are high in sodium, which should be avoided by anyone with high blood pressure.

COLD OR HOT?

THE temperature of water will have no significant effect on hydration levels, unless you drink very hot water on a hot day, which will make you sweat more.

iced water may help to increase consumption levels. A study by cardiff University published in 2013 said cold water is more palatable, perhaps because we evolved in hot climates and are hard-wired to enjoy a cooling drink. indeed, drinking iced water does help endurance athletes to keep going, say researchers in Australia. They found it effectively lowers exercisers’ core temperatures so they sweat less and keep hydrated better, according to a study i n Sports medicine in 2012. if you suffer migraines, though, you may be best avoiding iced water.

cold water significantly increases the risk of migraines and other headaches, particularly in women, warn neurologists at Sweden’s Uppsala University Hospital.

it is believed the sudden impact of cold water on the roof of the mouth causes blood vessels to the brain to dilate, sending warm blood to protect it. This creates pressure i n the brain that can trigger a migraine.

HOW ABOUT TEA AND COFFEE?

IT’S a long-held belief that drinking lots of caffeinated tea and coffee makes you go to the toilet more often. But there is scepticism over this in the science world.

A recent study Ann Grandjean, president of The Human Nutrition centre at the University of Nebraska, compared tea and coffee drinkers with people who drank the same quantities of water.

Tests on their blood and urine outflow found no difference in their overall levels of hydration.

Other studies have found the diuretic properties of tea and coffee to be minimal at best.

it is best to avoid drinking alcohol, however, because it is a diuretic. Studies show that if you drink 200 ml (third of a pint) of beer, you pass 320 ml (half a pint) of urine.

HOW MUCH IS TOO MUCH?

IF WE drink more water than our kidneys can process, it stays in our body and dilutes sodium levels.

This causes hyponatremia or water toxicity — an imbalance of electrolytes important for the cells in the body to function.

This is seen in babies who drink several bottles of water a day or infant formula that’s too diluted.

Water intoxication can also afflict athletes, causing a condition called exercise-associated hyponatremia.

This can prove fatal. in 2008, Andrew Thornton, 44, of Bradford, died from drinking ten litres — more than 17 pints — in eight hours to relieve painful gums.