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Why is too much water dangerous?

The Magazine answers...

Water droplet
Water can cause the brain to swell
A Californian woman has died after taking part in a water-drinking contest, but why is too much water dangerous?

We are regularly advised to drink more water: it clears skin, reduces tiredness and aids concentration.

But the death of a woman in the US after taking part in a water-drinking contest shows you can have too much of a good thing.

Jennifer Strange had taken part in the "Hold Your Wee for a Wii" game, which promised the winner a Nintendo Wii. Afterwards she reportedly said her head was hurting and went home, where she was later found dead. Initial tests have shown her death is consistent with water intoxication.

Drinking too much water can eventually cause your brain to swell, stopping it regulating vital functions such as breathing, and causing death. So what happens?

BBC graphic
A feature to the BBC News Magazine - aiming to answer some of the questions behind the headlines

Water enters the body when we drink and is removed primarily in the urine and sweat. The amount of water in the body is regulated to control the levels of certain compounds, such as salt, in the blood.

If you drink too much water, eventually the kidneys will not be able to work fast enough to remove sufficient amounts from the body, so the blood becomes more dilute with low salt concentrations.

"If you drink too much water it lowers the concentration of salt in your blood so that it is lower than the concentration of salt in cells," says Professor Robert Forrest, a consultant in clinical chemistry and forensic toxicology at the Royal Hallamshire Hospital in Sheffield.


The water then moves from the dilute blood to the cells and organs where there is less water. Professor Forrest likens this to the effects seen in science-class experiments.

Anthony Andrews
Actor Anthony Andrews was treated for water intoxication in 2003
"If you put salty water on onion skin the cells will shrink, if you put too much water on it the cells will swell," he says.

This swelling is a problem in the brain.

"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."

Eventually these functions will be impaired and you are likely to stop breathing and die. Warning signs included confusion and headaches.

Symptoms would normally occur very soon after drinking the water, but if the gut is absorbing the water more slowly then it can take longer.

Drinking several litres over a relatively short period of time could be enough to cause water intoxication. Those most at risk include people taking ecstasy, as the drug increases thirst and facilitates the release of anti-diuretic hormones so more water is taken in but cannot be excreted. Also, elderly people because their kidney function may be impaired.

Treatment for drinking excess water is "relatively straightforward", says Professor Forrest. It includes giving patients diuretics to help decrease their water load, or using drugs to reduce the swelling caused by excessive water.


He says the real problem is diagnosis. Because patients can be very confused they are often mistakenly thought to have taken drugs.

Ursula Arens, of the British Dietetic Association, says water is essential for a variety of bodily functions, for example to excrete waste products such as urea.

We lose water all the time and so need to replace it and in normal circumstances should aim to drink about one and a half litres every day, she says. During hot weather or exercise more should be consumed as dehydration can lead to bad breath, tiredness and a higher risk of bladder infections.

"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," she says, but adds that drinking too much water is unusual.

Below is a selection of your comments.

A partner of mine was a nurse, and I remember him telling me over 20 years ago that "The poison is the dose". This death illustrates the truth of that statement as clear as a bell.
Stephen Watson, Brighton, UK

I believe that when drinking too much water, the water is absorbed into the red blood cells which causes them to swell also, so if there is too much water, there is a possiblity that the red blood cells will explode.
Bob, East Grinstead

I recently looked this up on web to find out how much water an adult should drink per day. The problem was that some sites, like the above report, say to drink 1.5 litres per day, whilst others say 2, 2.5 or even 3 litres per day. All recommendations appear to have been made by experts so who should we believe? Very confusing?
Mike Griffiths, Clydebank - Scotland

What has happened to this poor lady (and her family) is an absolute tragedy. Water intoxication is something that many people pooh-pooh as nonsense, but here is absolute proof it exists. Some of the deaths attributed to class a drugs, such as ecstacy have also been caused by the deceased having taken in too much water, but no-one believes it can be true, because water can only be 'good for you'. This Jennifer Strange, all for the sake of some new, five minute, flash in the pan, toy...for God's sake. Rest in peace.
Hazel, Hove

Yet another person harmed due to their own greed and the event coordinators stupidity. There have been a number of cases similar to this such as the person who got third degree burns after sitting on ice for money as well as the woman who got her forehead tattooed as part of a competition. All trying to get something for nothing...
Sam, Guildford, Surrey

A needless and tragic death of a young mother, all for a video game? Tragic.
Jenny, Dublin, Ireland

Ironically, long distance runners have to be careful of drinking too many fluids!; the feeling of thirst does indicate de-hydration, but serious athletic performance can mislead you. Holding in fluids for several hours can cause confusion, headaches and is detrimental to athletic performance. Several marathon runners have died to due over consumption of fluids.
Richard Elliott, Bradford

I just guess as the saying goes"too much of everything water inclusive is bad"keep up the good work
tijani sadiq, lagos,nigeria

Tragic, as these cases always are, but also a clear warning to people not to be so stupid! Nothing that we can and do ingest is good for us in unlimited quantities - surely that should be clear to everyone. Sadly, it appears not to be. Water is so innocuous, so normal, so recommended. Yes, but don't people ever ask WHY they have to drink water? I suppose none of the reported victims had ever bothered to think about why we need water.
D. Fear, Heidelberg, Germany

It is curious how the message has crept into society that one needs to drink four litres of water a day. I am sure this has been put out by the bottled water industry. In a temperate climate like the UK, the body's own regulatory system easily copes with fluid balance and forcing extra water into the body is useless and maybe detrimental.
Bob Gardiner, Kirkbymoorside

This is really shocking. My brother joined the Para's last year and as part of one ofthe 'beasings' he got during the training period, was for the guys to drink as much water as possible. They drank water until and after they were sick where they were standing! This knowledge should be more widely spread.
anon, surbiton, Surrey

So i take it we'll be seeing "Dummy's guide to drinking water" out in the shops anytime soon?
Tom Taylor, Warrington, UK

Did the people running this stupid contest know this? Should there not have been health warnings to the contestants? theyre close to murderers if there was't, i sincerly pray for the poor woman who wanted the gameconsole that everyone seems to own. Capitalism at its best and love to her family at this time. The preponderence of lawyers around no doubt will help them work in a court of law against the contest runners.
ellenore jayne stemp, cambridgeshire UK

It's a problem that doesn't really attract the attention it deserves. The same problem happens if you sweat a lot or have the runs, and fail to replace the sodium or other vital minerals in your body. Hence why we have rehydration fluids, and not just water!
Ed, London

Jeremy, London

I was told to drink 3 litres a day to flush out kidney stones. This was very hard work though I was told that this was the best way to get rid of them
michael blake, Plymouth England

There is so much misinformation about water intake here in the US, and you see people walking around with their personal water bottles everywhere! For example, everybody seems to repeat the "eight cups a day" mantra [a US cup is 8 fl. oz.], even people who should know better! In fact you need about 8 cups *including the water you get from your food*. For most people that means about only 4 to 6 cups of liquid are needed (even apparently dry foods like bread contain some "free water") -- so leave the sippy cups at home if you are over 4 years old, OK? Another big myth is that caffeinated drinks don't count -- also not true. Coffee, tea and coke do have some diuretic effect but you should still count them as about half to two-thirds their actual volume.
Carl, USA

Given the very sound scientific knowledge upon the risk of drinking too much water in a short period of time as clearly explained above, the Californian authorities should consider prosecuting the organisers of the contest for not ensuring that participants were fully informed and adequately looked after.
Richard Little, Cambridge

Interestingly, marathon runners have known about the risks of drinking too much water for a while since there were a few deaths on the marathon circuit of people who had drunk too much water during the marathon itself. People were loading up on water before the marathon and assuming that they would sweat out the excess water during the marathon in order to avoid dehydration. The problem during a marathon is not one of high water levels but really one of low sodium levels. The heat generated by the body during exercise naturally makes the runner sweat, but the sweat contains high levels of salt which is not replaced in the body by drinking water either before or even during the race. This is the reason that all marathons now offer sports drinks, that contain salts and minerals to replace the sodium / magnesium / potassium that is sweated out during the race. So sports drinks that advertise themselves as being isotonic are not just gimmicky but serve a very real purpose.
David Harrison, Clitheroe, Lancashire

This is all really confusing. We have always been told that drinking lots of water is good for us and that it is good if your urine is clear but now we are being told that is actually a bad thing. I recently read that if you are thirsty, you are already dehydrated so you should drink enough that you don't get thirsty but this may mean you are drinking too much. While this sort of tragic accident seems to be the exception and not the rule, it is very scary that something that seems so benign like drinking lots of water can be deadly.
Mel Low, London, UK

"If you are going to the toilet more than once every few hours or so that might be too much, especially if your urine is clear," Well that means every time I have a few pints why I behave so strangely. I thought I was drunk, but it must be water intoxication!
Joe Delaney, Ladbroke Grove, London

"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," This is also a symptom of Diabetes, excessive urination coupled with excessive thirst. If this does occur get checked by a doctor, don't wait
Mike Abbott, Kettering

Is it known exactly how much water this woman drank in this contest? Obviously drinking ample water IS a good thing, but I'm curious as to how much this woman consumed in order to die; as I'd imagine it would have to be huge quantities to cause such a lethal effect to her circulatory system.
R Reynolds, Bristol


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