Even Mild Dehydration May Change Mood, Ability to Think

An inability to think clearly, a feeling of being ‘cranky’ and tired, and a lagging energy level can be caused by mild dehydration according to researchers of the University of Connecticut.

It is true that a marathon runner can lose up to 8 percent of their body weight when they compete, but the study, published in the British Journal of Nutrition, showed office workers and students can be adversely affected too. It says that just 1.5 percent loss in normal water volume can have an impact even on people who are sitting at rest.

“Our thirst sensation doesn’t appear until we are 1 or 2 percent dehydrated,” said Professor Lawrence Armstrong, "by then dehydration is already…starting to impact how our mind and body perform.” He added that, "Staying properly hydrated is just as important for those who work all day at a computer as it is for marathon runners.” Researchers monitored two groups of young men and women, described as "healthy, active individuals who were neither high-performance athletes nor sedentary—typically exercising for 30 to 60 minutes per day.

They took cognitive tests measuring vigilance, concentration, reaction time, learning, memory and reasoning while mildly dehydrated—either from gentle walking or simply being sedentary without drinking water. These results were compared with tests when subjects were not dehydrated.

Young women experienced fatigue, headaches and difficulty concentrating. Tasks were perceived as more difficult, though there was no reduction in their cognitive ability. In men, mild dehydration caused decline in vigilance and working memory. Researchers reported that young men also felt fatigue, tension and anxiety when mildly dehydrated. Adverse changes in mood and symptoms were substantially greater in females than males, at rest and during exercise.

Research was conducted with the U.S. Army Research Institute of Environmental Medicine and several U.S. universities. A psychologist with the Military Nutrition Division of the Army Research Institute said the adverse mood changes in both sexes "may limit the motivation required to engage in even moderate aerobic exercise."

—Reported by Patric Hedlund

This is part of the February 24, 2012 online edition of The Mountain Enterprise.

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