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Drink More Water
A 2012 study in The Journal of Nutrition found that mild dehydration (so subtle that you don't really feel it) can lead to inattention. When women were less than 2 percent dehydrated (in this case, from not drinking enough water after exercise), their ability to concentrate on a series of cognitive tests was impaired. "When the brain detects even the smallest changes in physiology, it may begin operating at a suboptimal level to get your attention," explains study coauthor Harris Lieberman, PhD, a research psychologist at the U.S. Army Research Institute of Environmental Medicine. "Thirst is not the best measure of hydration, so a decrease in your ability to focus is an early warning signal that it's time to drink up."