Blog | Wednesday, August 17, 2011

Do you really need to drink a half gallon of water each day?

"It's good to know that glasses
are what can help us drink;
The trouble is, we don't know
What is the purpose of thirst."

--Proverbios y cantares.XLI. Antonio Machado

The one thing you can't afford to have missing when you start a scientific congress or any other professional meeting is not a notepad, a pencil or even an iPad, nowadays, it's a bottle of water. Offices, airports, handbags and lecture halls, all of them are bursting with all kinds of bottles. It seems they are essential to work and even to stay alive.

Black glass of water by Luca Venturi Oslo via Flickr and a Creative Commons licenseBordering nonsense, some people desperately search for a bottled water vending machine as soon as they arrive at the airport, even if that means gobbling it down in a minute before walking through the security checkpoints.

It is now a common belief that continuously drinking water (6 to 8 glasses a day according to NHS, at least two liters, or half a gallon, according to other sources) is the healthy thing to do.

There is even the Hydration for Health initiative, seeking to promote water consumption, and it has its own annual meeting. Wonder where is it held? In Evian, France, incidentally not only a town but also a famous brand of bottled water. Who sponsors the meeting? Danone, a company that has several bottled water brands among its most profitable products. It's hard to know how big the industry is, but British Bottled Water Producers' own website makes it clear it is a thriving business, with more than 33 liters of per capita yearly consumption only in the U.K. and growing every year.

There is nevertheless no evidence whatsoever that getting healthy people to drink more water will lead to something else than more profit for the manufacturers and their shareholders. Margaret McCartney, a GP from Glasgow, is the author of Watterlogged?, a sharp text on this subject published in the British Medical Journal. She reviews all the arguments to back this water craze and checks it with scientific evidence published in well-established peer-reviewed journals (there are of course many articles favorable to water in other, pseudo-scientific magazines backed by industry money). Her final conclusion is that there is no solid evidence to advise anybody in good health (even a child or an old person) to drink if he/she is not thirsty.

McCartney also depicts an interesting anecdote: Professor Stanley Goldfarb, MD, published a 2008 editorial in the Journal of the American Society of Nephrology with the same conclusion: there is no scientific proof that drinking water will make you healthier. A short time after that, two Danone executives invited him to dinner. McCartney writes that those men "didn't try to make him change his point of view, but did confidentially show him some charts that proved a sales fall right after the publication of his editorial".

It's only logical that companies try every ruse to sell their products. What is not so logical is that official institutions that meant to be neutral, that are supposed to safeguard the health of the population taking state-of-the-art scientific evidence into account (whether those institutions are NHS, a Ministry of Health or a regional authority) spend their time spreading unfounded habits just because they assume anything involving prevention must be intrinsically good.

The result is that the same departments that are committed to fight climate change and protect environment are increasing both water consumption and waste generation (as this drinking water is mostly bottled).

My personal take on this is to say "Thank you, but no thank you" every time I'm offered bottled water at a meeting. In this case, Machado's words were wrong. Thirst does serve a purpose. It lets us know when to drink.

This post by Sergio Minue, MD, appeared at Get Better Health, a network of popular health bloggers brought together by Val Jones, MD. Better Health's mission is to support and promote health care professional bloggers, provide insightful and trustworthy health commentary, and help to inform health policy makers about the provider point of view on health care reform, science, research and patient care.