London - Sophie Ruffles was running her third half marathon when she decided to take a gamble and not drink during the race.
“I’d queued for the loos during previous runs and it was a pain, so I thought I’d skip the water stops. I figured I was young and fit and would be okay,” she says.
Sophie, a 33-year-old solicitor from Bristol, had water an hour before the race, but didn’t drink again during it.
“But it was hotter than I’d expected and I started to sweat a lot, more than usual,” she says. “I was fine for most of the course, but as I reached the final 600m I felt dizzy and staggered, then just blacked out and hit the ground.
“I was out cold for less than a minute, but when I woke I couldn’t remember my name or where I was. It was really scary.”
After 20 minutes, her legs were like jelly but she made it over the finishing line, only to faint again. She was taken to the paramedics’ tent, where she was told she was severely dehydrated.
“I was talking gibberish. I hadn’t realised how serious the consequences could be. It shook me up as I run alone and I worried about fainting and falling in front of a car.” She had to take the next two days off work.
Dehydration is defined as a one percent or greater loss of body weight through fluid loss, but you feel thirsty only when you have lost 0.8 to 2 percent of body weight, by which time you are already dehydrated. Sophie now carries water on every run.
If you don’t think Sophie’s experience could apply to you, think again. Research published recently by Loughborough University found that dehydrated drivers were as dangerous as drunk drivers.
Drivers who had only 25ml (just under two table spoons) of water an hour made twice as many driving errors as drivers who were well hydrated. The researchers said dehydration can affect cognition and alertness, as well as causing headaches and fatigue.
Dehydration is a growing problem. Emergency hospital admissions for dehydration have risen by 57 percent over the past decade.
Some of that rise can be attributed to an ageing population: older people are more likely to become dehydrated for various reasons, including having a less sensitive thirst mechanism due to the effects of ageing.
However, nearly a fifth of admissions were in the under-60s.
Tom Sanders, professor emeritus of nutrition and dietetics, King’s College London, says busy lifestyles may be partly to blame for people not drinking enough.
Professor Sanders, who advises the Natural Hydration Council, a not-for-profit organisation funded by the bottled water industry, says: “Traditionally, people would stop for a tea break mid-morning and have a proper lunch hour when they topped up their fluid levels, but this has been eroded.
“We have got this habit of grabbing a coffee on the go, but strong brews such as espresso have very little water and will also make you pass urine because caffeine has a diuretic effect.”
The European Food Safety Authority (EFSA) recommends men have two-and-a-half litres of fluid a day, and women two.
Around 70 to 80 percent of this should come from drinks and the rest from food, says Dr Emma Derbyshire, a senior lecturer in physiology at Manchester Metropolitan University. If you exercise, you need extra fluid: roughly a large glass of water (200ml) for every 45 minutes of exercise.
“According to one survey, 60 percent of the population drink at least one glass of water a day and 80 percent drink no more than two,” says Dr Derbyshire.
“Another survey we carried out with the internet group Netmums found one in four mothers said their child went to school without a drink in the morning; which means they could have gone without a drink for 18 hours.
“Studies show dehydration in children leads to poor concentration and behavioural problems.”
It doesn’t have to be water that makes up your daily fluid intake.
“Tea and coffee are fine, but they contain caffeine, which means a lot of them can have a dehydrating effect,” says Dr Derbyshire. “But water is healthiest; it’s calorie and fat-free.”
You can be affected in a surprisingly wide range of ways by a lack of fluid, says Dr Roger Henderson, a Shropshire GP.
“Water is central: it helps to regulate body temperature, carries nutrients and oxygen around the body in the blood, lubricates joints, prevents constipation, as well as moistening soft tissues and producing saliva.
“If you don’t have enough, it’s like not having petrol in the car.”
Early symptoms of dehydration include feeling tired and fatigued, a dry mouth, poor concentration and light-headedness as well as darker, stronger smelling urine.
Being dehydrated can also trigger migraines, says Dr Fayyzad Ahmed, a consultant neurologist at Hull Royal Infirmary and spokesman for the Migraine Trust.
“If you don’t have enough fluid, the blood becomes thicker and this leads to the hypothalamus, the area of the brain responsible for a number of bodily functions, triggering the thirst sensation.
“If you ignore that thirst reflex, the hypothalamus can generate symptoms to tell you something is wrong. One of these is migraine, others are lethargy and tiredness.
“Most people will take a painkiller but simply rehydrating may be enough.”
Dr Henderson says he is seeing more cases of people with milder signs of dehydration.
“Feeling tired all the time is a frequent complaint, as well as headaches and urinary tract infections such as cystitis,” he says. “I always ask people how much they drink. In a significant number of cases, their tiredness, headaches and urinary tract infections are at least partly due to chronic dehydration.”
Water is thought to flush out bugs from the bladder, so if you are dehydrated, they are more likely to hang around, causing infection.
Dehydration can also contribute to kidney stones, says Matthew Bultitude, a consultant urologist at Guy’s and St Thomas’ Hospital, London. They form when urine is too concentrated and minerals, such as calcium, crystallise.
The number of people in hospital for kidney stones rose by 63 percent between 2000 and 2010.
“We tell our kidney stone patients they need to be producing a minimum of 2½litres of urine per day (we ask them to measure output in a plastic jug) and to achieve this they need to take in 2½ to three litres of fluid,” says Bultitude.
“To some extent, though, how much water you will need will depend on your lifestyle and your environment; we have a lot of chefs with kidney stones because they work in hot environments and don’t drink enough. For them, three litres of water a day might not be enough.”
Dehydration can also contribute to dry eyes, where they feel tired, gritty and vision may be blurred, says Francesca Marchetti, of the College of Optometrists. “Keeping yourself hydrated helps with dry eyes, as it is like any other mucous membrane. Lips get dry when you’re dehydrated; your eyes are the same.”
Fluid intake is also important for the skin. Justine Hextall, a consultant dermatologist with Western Sussex Hospitals NHS Trust, says that it helps to plump up the skin.
“If you’re dehydrated, your skin tends to be drier and wrinkles more noticeable.”
You might get dark circles under your eyes: the skin is thinner and because it is concave it does not reflect light as well.
To see if you are dehydrated, pinch the skin on the back of your hand; if it falls back more slowly it means that you are probably already dehydrated.
While being slightly dehydrated won’t make you critically ill, it may worsen the effects of other medical conditions, says Dr Henderson.
“People with diabetes are at risk of kidney problems and if they’re dehydrated this could put extra pressure on their kidneys.”
In more severe cases, dehydration causes a rapid heartbeat, low blood pressure, not passing urine, feeling confused, a weak pulse, sunken eyes, cool hands and feet and seizures.
These symptoms need urgent medical attention: rehydration on an IV drip in hospital.
Dr Patricia Macnair, a specialist in medicine for the elderly at Milford Hospital, Surrey, says it is mainly the elderly who suffer from severe dehydration.
“Older people may also lose the urge to drink and perhaps physically can’t get a drink. If they develop dementia they may lose the understanding or motivation to take regular drinks,” she says.
Older people may also be on diuretics (water tablets) and aren’t drinking enough, or are taking painkilling drugs such as tramadol, which can make you feel drowsy so you don’t feel like drinking or eating, says Dr Chris Fox, consultant old age psychiatrist at Norfolk and Suffolk Mental Health NHS Foundation.
Most workplaces have water coolers and people carry water bottles.
However, not everyone agrees that we need to drink so much water. Catherine Collins, a dietitian at St George’s Hospital, South-West London, says too much fuss is made about the perils of dehydration.
“Staying well hydrated is important for health, but thirst is a very powerful mechanism and it is not just water that will hydrate you, but any liquids, including tea and coffee and even beer (spirits won’t, though),” she says.
She is also not convinced that caffeinated drinks are a problem in the way some experts claim.
“There is this perception that caffeinated drinks will make you go to the loo more,” she says.
“While it is true that if you do not normally drink caffeine, a strong coffee will temporarily increase your urine volume. But for those used to caffeine, it is the volume of the drink, not the caffeine content, that will do this.”
Daily Mail