Your Brain On Dehydration

It doesn’t take long for dehydration to render us even less focused than we normally are. Two hours of yard work will do the trick. A Georgia Tech news release reports that researchers at the school came to that conclusion after reading many research papers on dehydration and cognitive ability. The data suggests that functions like attention, coordination and complex problem solving suffer the most, and activities like reacting quickly when prompted diminish to a lesser extent.  “Maintaining focus in a long meeting, driving a car, a monotonous job in a hot factory that requires you to stay alert are the kind of situations in life that challenge attentiveness,” says Millard-Stafford, the study’s principal investigator. “Higher-order functions like doing math or applying logic also dropped off.” The researchers found no hard and fast rule about when exactly such lapses begin, but after examining studies with 1 to 6 percent loss of body mass due to dehydration, they found more severe impairments started at 2 percent. How do we know when we reach 2 percent? “If you weigh 200 pounds and you go work out for a few of hours, you drop four pounds, and that’s 2 percent body mass,” says Millard-Stafford. “With an hour of moderately intense activity, with a temperature in the mid-80s, and moderate humidity, it’s not uncommon to lose a little over 2 pounds of water. If you do 12-hour fluid restriction, nothing by mouth, for medical tests, you’ll go down about 1.5 percent,” she says. “Twenty-four hours fluid restriction takes most people about 3 percent down. If you drop 4 or 5 percent, you’re going to feel really crummy. Water is the most important nutrient.”