Sunday Rerun: Have a drink

 When your doctor or fitness coach or spouse tells you to drink more water, it's not that they own a huge chunk of Poland Spring stock. The fact is, the water that comes right out of the tap, or garden hose, will do, but the trick is you have to DRINK it!  A lot of people lug home 35-packs of bottled water, or fancy glass bottles of mountain-fresh water just down from the majestic Lake Sopchocky Falls.

Just owning water is not good enough. You actually have to drink it.

And there is more and more evidence that being even a bit dehydrated can scramble your mood -  or your noodle.

Mindy Millard-Stafford, director of the Exercise Physiology Laboratory at Georgia Institute of Technology, reports finding that, "When people are mildly dehydrated they really don't do as well on tasks that require complex processing or on tasks that require a lot of their attention."  She's done 33 studies on this, and published her analysis of the evidence this month, right after she drank a whole lot of water.

And this time of the year, with people inexplicably taking to the great outdoors to get that 20-mile run in, is even harder to deal with, because with summer heat and humidity, it does not take long at all to become even mildly dehydrated.

"If I were hiking at moderate intensity for one hour, I could reach about 1.5 percent to 2 percent dehydration," reports Doug Casa, a professor of kinesiology at the University of Connecticut, and CEO of the Korey Stringer Institute.

2 percent dehydration means you've perspired about a liter of water.

"Most people don't realize how high their sweat rate is in the heat," Casa adds, pointing out that it only might take a half an hour to soak out that much water.

And the problem there is, just as you might keep eating before your "appestat" tells you "that's enough chow!" you might be reaching dehydration before you even feel thirsty.

But you can tell the effects on your mental performance almost right away.

Nina Stachenfeld, of the Yale School of Medicine and the John B. Pierce Laboratory, led research into this, testing a group of young healthy women who took cognitive tests, and cut their fluid intake to 6 ounces a day. That was a 1% dehyrdration, and even that small amount showed a measurable effect on their mental flexibility.

The test was a card game that required the women to deal with rule and situation changes, and sure enough, when they weren't getting enough water, they make lots more mistakes.

And then, given all the water they cared to guzzle, they went back to doing well in the game.

The tests showed that even coffee or tea - drinks made with water - had the same salubrious effect, so from Starbucks to Lipton to Aquafina, whatever it is, drink up!

The next part of the test - locating public restrooms - is still being analyzed.