Over the last few weeks, those who visited the British Medical Journal's website might have noticed an advert for a new public health initiative, Hydration for Health. It is sponsored by Danone – which owns the Evian, Volvic and Badoit bottled water brands – and urges healthcare professionals to encourage people to drink more water, claiming that "evidence is increasing that even mild dehydration plays a role in the development of various diseases".
Margaret McCartney, a GP and columnist, saw these adverts and complained about it, writing an article for the BMJ (who admitted "we hadn't followed our own guidelines. The advertisement bypassed our editorial checks") about the lack of evidence – and citing the shortcomings of many studies – that people should be drinking more water. "I prefer to get my health information from unbiased sources rather than people with vested interests," she says. The idea that we should drink eight glasses of water a day is expounded, among others, by the NHS Choices website. "This is not only nonsense," writes McCartney, "but thoroughly debunked nonsense."
But you can see the drive to get people to drink more water in other places, too. In the Royal College of Nursing's "hydration toolkit", its best practice guidance – produced, incidentally, in conjunction with Water UK, which works on behalf of the water industry – it makes the sensational claim that by drinking water you "will also be helping to protect yourself against three of the biggest killer cancers [bowel, breast and prostate]". Much further down the report, and far less noticeable, it states, "the benefits of good hydration to protect against cancer have not been well studied and the current findings are considered to be inconclusive".
Many of us have been led to believe that the more we drink, the healthier we will be. At the weekend, in his column for the Sunday Times, Dominic Lawson outed his sister Nigella as an "aquaholic", drinking several litres a day. Several newspapers followed this up this week by interviewing women who drank excessive amounts of water thinking they were doing themselves good – one, Joanne Jarvis, interviewed by the Daily Mail, was hospitalised after drinking 11 litres over four hours.
When did we become so fearful of dehydration? Schoolchildren are encouraged to take bottles of water into classrooms and sip them throughout the day. Peer into most meeting rooms in the country and you will see bottles of water planted on the table in front of executives, as if they fear that the slightest dehydration will impair them in some way. At the gym, people replenish water as fast as they sweat it out.
A few years ago, Stanley Goldfarb, professor of medicine and a kidney specialist at the University of Pennsylvania, noticed a strange phenomenon. "People were dragging around big bottles of water with them and drinking all the time and I thought: 'What are they doing?'"
He says on the phone from his office in Philadelphia: "Since we have a perfectly good system to alert us if we need water, why would you need to subvert that by drinking in a prophylactic way?" He reviewed the scientific literature on the health benefits of drinking a lot of water, identifying the four recurrent themes that were put about by those who advocated it.
"One was that water improves your skin," he says. "We showed there was no scientific basis for that. The second myth is that drinking water is an aid to diets and would reduce your appetite. That has been carefully studied and it doesn't. If you flavour the water, that will suppress your calorific intake during the subsequent meal, but nobody has shown that it suppresses it over 24 hours. When you finish the meal and you didn't eat enough calories, you're going to be hungry, and you'll eat later. We said there really is no evidence that going on a water-drinking campaign will lead you to lose weight."
The third myth he looked at is that drinking water flushes more toxins out of your body. "All it does is increase the volume of your urine, but it doesn't change the material in the urine. The last issue that people have advocated is that water can control headaches. It was not substantiated."
When we need water, he says, the brain releases a hormone "in response to dehydration that tells the kidney to reduce its excretion of water. This hormone is suppressed whenever there is more water than the body needs, and the kidney immediately unleashes its ability to excrete water, which is dramatic. The body has this system for regulating amounts of water. The way you're told to drink water is you become thirsty, and you become thirsty well before there's any impairment that dehydration might induce."
Elderly people may have an impaired thirst sensation and need to be reminded to drink, he says. "The other group that needs to drink a lot of water are people who suffer from kidney stones, because it has been shown to reduce the risk of kidney stones. But other than that, there is very little evidence that drinking a lot of water is useful."
Neil Turner, professor of nephrology at the University of Edinburgh, and president of Kidney Research UK, says: "Nobody who is in reasonable health needs to have any concern about drinking enough water because their body will tell them." Drinking too much can be harmful, but this is rare. "The times people can be caught out is if they suddenly drink a huge amount of water. The ones that have come to public attention have been related to people running marathons who overdrink, or people drinking water with ecstasy because of the worry about dehydration."
The well-publicised death of the British teenager Leah Betts in 1995 was caused by the huge amount of water she drank after taking an ecstasy pill. In 2007, David Rogers, a fitness instructor, suffered hyponatraemia – water intoxication – and died after drinking too much water after his first London marathon. "It dilutes the things that are normally in blood, particularly sodium, and that is associated with having fits and passing out. But this would have to be extreme drinking; it's not something that people drinking ordinarily have to worry about."
According to the European Food Safety Authority, healthy adult women need two litres a day, and men around 2.5litres. We get around 20% of our water from food. "What people don't realise is that even dry food such as cheese contains a fair amount of water – about a third by weight," says Catherine Collins, spokesperson for the British Dietetic Association. "And obviously fruit and vegetables are virtually all water." Tea, coffee, juice and milk all count towards the total – it is a myth, she says, that tea and coffee are diuretics if you are accustomed to caffeine. Eat five portions of fruit and vegetables a day as a part of a balanced diet, and drink when you're thirsty, and you will meet your water needs, she says. "Our kidneys are exquisitely poised to retain fluid if we are getting dehydrated. [Bottled water companies] are keen to exploit the idea that we are constantly balanced on a pinpoint between hydration and dehydration."
So where did the eight glasses a day idea come from? In his 2002 study debunking the 8x8 message – eight glasses, containing eight ounces (around 235ml) of water – Heinz Valtin, a kidney specialist at the Dartmouth Medical School in New Hampshire, traced it to an American nutritionist Frederick J Stare, and a passage in a 1974 book he co-wrote: "For the average adult, somewhere around 6 to 8 glasses per 24 hours and this can be in the form of coffee, tea, milk, soft drinks, beer, etc. Fruits and vegetables are also a good source of water."
Valtin writes: "Given Dr Stare's leading position in the field of nutrition, it is conceivable that 8x8 began with this apparently offhand comment." It could also have originated in a 1945 report from the Food and Nutrition Board of America's National Research Council, which advocated "one millilitre [of water] for each calorie of food.
Most of this quantity is contained in prepared foods. If an average person consumes around 2,500 calories, this translates to two and a half litres. The part about us getting a proportion of this naturally from our food was forgotten and the two litre message seems to have stuck.
It is this that the bottled water industry seized upon. Just look to the Natural Hydration Council – a body set up by the biggest producers Danone, Nestlé and Coca-Cola to promote sales of bottled water over sugary soft drinks, which curiously, they also own – and its tagline "you ought to drink more water". The Natural Hydration Council has recently been visiting NHS healthcare staff to extol the values of drinking water.
"What people don't need to do is take in two extra litres a day," says Goldfarb. "You're going to take in two litres a day based on your diet and thirst sensation. What [bottled water companies] are really asking people to do is take in four or five litres, because they're already taking in two or three as coffee, tea, soft drinks, fruit, alcoholic beverages – that's all water. This notion is a marketing ploy."
The market for bottled water started to take off in the 1980s. In the US, the Beverage Marketing Corporation published its first report into the bottled water market in 1983, while in the UK, the distinctive green glass bottles of Perrier became a yuppie dinner party cliche. In the 90s, small plastic bottles became more prevalent and celebrities were photographed with them. Bottled water became a lifestyle choice and a fashion accessory. Stars such as Jennifer Aniston claimed their "beauty secret" was several litres of water a day, and magazines advised to drink at least two litres of water to "flush out" toxins.
The market grew at an extraordinary rate. Today, around 56bn gallons of bottled water are sold every year, and the market is worth £25bn, with huge corporations owning many of the best-selling brands. In the UK, Nestlé owns Perrier, Buxton, Vittel, San Pellegrino, Acqua Panna and Nestlé Water. Danone has Volvic and Evian, and Coca-Cola owns Abbey Well under the Schweppes brand, and until it closed it down last year, Malvern water, the bottled water the Queen liked to take on her travels.
When the market became saturated, new products had to be different to stand out and "luxury waters" were launched. You can buy bottled Australian rain water (Cloud Juice) and water from Canadian glaciers (10 Thousand BC) that is, apparently, bottled to the sound of "inspirational music", because water has, according to the company, "a memory". Bling H2O, vying to be the most expensive water in the world, brought out a bottle covered in crystals for around £1,600 (even a simple small plastic bottle costs around £12). In its marketing, the company makes the unintelligible boast that its water is in "a Haute water bottle so beautiful that it could stand alone on the Global red carpets of the world [sic]." Restaurants started employing water sommeliers, and Claridge's hotel in London introduced a water menu, with tasting notes.
More water-based products came out, claiming to offer different benefits. Vitamin-enriched and flavoured waters took off, though many of these contained almost as much sugar as a can of fizzy drink, despite their "healthy" packaging. Penta water said it was "the only molecularly restructured water on the market", claiming to contain smaller water molecules that could hydrate our cells faster – it was swiftly demolished by Ben Goldacre in this newspaper. It disappeared from the UK, but is still sold in America, where its website states that it "may help improve longevity of life". There is another brand, HydraCoach – each bottle costs nearly £25 – that even calculates how much you have drunk through its special straw, and reminds you to drink more if too much time has elapsed.
The recession and a possible backlash caused by the considerable environmental concerns surrounding bottled water have seen sales drop. According to Mintel's new report on the bottled water market, UK sales went down 16% between 2006 and 2009, and again in 2010, though at a slower rate – this was thanks to heavy discounting – and the research analysts are not expecting sales to pick up until 2014. But whether our obsession with drinking water – bottled or tap – is evolving into something more sensible remains to be seen. Aquaholics, however, please take note. "The National Academy of Sciences in the United States did a very extensive study several years ago assessing water intake," says Professor Goldfarb. I can hear the smile in his voice. "Their executive summary was: drink when you're thirsty."
