Tuesday, October 30, 2007

Water: 8 glasses a day is a myth

Everywhere you look, people are carrying plastic bottles of water....you see it at work, on the bus, in the theatre, in church(why?!)....it is as if we are living in a chronically dehydrated society in which people are dying of thirst....

What is going on? Partly I believe that it is a fashion thing. There is a tipping point process going on in which eventually it is the standard thing to be drinking lots of water. The science as far as I can see is fairly clear: the 8 glasses a day mantra lacks scientific proof and is basically an urban myth.

What is the harm of drinking lots of water?

"The fact is that, potentially, there is harm even in water," explains Valtin. Even modest increases in fluid intake can result in "water intoxication" if one's kidneys are unable to excrete enough water (urine). Such instances are not unheard of, and they have led to mental confusion and even death in athletes, in teenagers after ingesting the recreational drug Ecstasy, and in ordinary patients.

And he lists other disadvantages of a high water intake: (a) possible exposure to pollutants, especially if sustained over many years; (b) frequent urination, which can be both inconvenient and embarrassing; (c) expense, for those who satisfy the 8 x 8 requirements with bottled water; and (d) feelings of guilt for not achieving 8 x 8.

The full article is available here.

What got me thinking about this just now is a series that was posted recently in a blog I read regularly: The Science of Sport

They had an awesome series on fluid intake during exercise. The post here is a fascinating read, looking at how the accepted wisdom with respect to fluid intake has changed over the years.

Had you been around to run in the 1908 Olympic Games in Rome, you would be reading this with a sense of bewilderment at how things have changed. Today, runners are told to drink, drink, drink. Drink to replace ALL weight loss. Don’t get dehydrated, and so on. But your recollection of running in the early 1900’s would have been that you should NOT drink during exercise! Remarkably, 100 years ago, runners were being told by “experts” (that is, commentators on the sport and fellow runners) that drinking would be detrimental!
What changed things? The writers of this blog suggest that the problem really came about when sports drinks companies began sponsoring scientific research into sports drinks:

.......much of the research on the topic was funded by Gatorade, a company that produces sports drinks. The conflict of interests this created is staggering – an entire Institute, called the Gatorade Sports Science Institute, was created. A website, with a section dedicated to educating the public on fluid replacement needs, is sponsored by the company aiming to meet those needs. And perhaps not surprisingly, all the research of this time pointed in one direction – you need to drink, drink and drink. And when the marketing arm of the company used this information, they encouraged you to drink Gatorade!

This of course is not just a theoretical problem:
The problem, as we shall see in post 3 of this series, is that the excessive intake of fluid can cause the plasma be diluted to such an extent that a condition known as hyponatremia develops. And people die as a result of hyponatremia.
These studies continue today with things like the Lucozade Sport Science and Nutrition Centre. You just wonder how independent this science is. I am also reminded of the discussion recently about sports shoes. Marketing tells us one thing - you need these highly engineered shoes. Science says something different - such big shoes with all this cushioning etc. cause injuries rather than prevent them!

Fashion and Marketing...a powerful and potentially dangerous combination.

Art DeVany had a couple of excellent posts on this a couple of years ago:

Water Bottles, Sports Drinks, and Ancient Tastes

Follow up to Water Bottles

1 comment:

Anonymous said...

I can't speak for everyone else, but having a Nalgene glued to my hand was NOT a fashion statement (even though I carried it to work and to church.)

I used to NEED that water...and then I went paleo. I was shocked to see that two of the three bottles I carried to work sat full at the end of the day after a few days of paleo eating. I now believe that epidemic dehydration is a direct result of the carb and grain freebasing practiced by the unwashed masses.