We all experience feeling cranky without reason from time time. And this might happen when everything in life is going well. Interestingly, the low energy levels and the blues may not have an emotional reason, but a physical one. According to research by experts at the University of Connecticut's Human Performance Laboratory, even mild dehydration [1.5 per cent loss in the body's water volume] can alter a person's mood, energy level, and ability to think clearly.
It doesn't t matter if a person has just walked for 40 minutes on a treadmill or has been sitting—the adverse effects from mild dehydration are the same. "Dehydration affects all people, and staying properly hydrated is just as important for those who work all day at a computer as it is for marathon runners, who can lose up to 8 per cent of their body weight as water when they compete," says Lawrence E. Armstrong, one of the studies' lead scientists and a professor of physiology in UConn's Department of Kinesiology in the Neag School of Education. He is also an international expert on hydration who has conducted research in the field for more than 20 years.
"Our thirst sensation doesn't really appear until we are 1 [per cent] or 2 per cent dehydrated. By then dehydration is already setting in and starting to impact how our mind and body perform," says Armstrong.
For the study, separate groups of young women and men were tested. Twenty-five women took part in one study. Their average age was 23. The men's group consisted of 26 men with an average age of 20. All of the participants were healthy, active individuals, who were neither high-performance athletes nor sedentary—typically exercising for 30 to 60 minutes per day.
Each participant took part in three evaluations that were separated by 28 days. All of the participants walked on a treadmill to induce dehydration, and all of the subjects were hydrated the evening before the evaluations commenced. As part of the evaluation, the subjects were put through a battery of cognitive tests that measured vigilance, concentration, reaction time, learning, memory, and reasoning. The results were compared against a separate series of tests when the individuals were not dehydrated.
In the tests involving the young women, mild dehydration caused headaches, fatigue, and difficulty concentrating, according to one of the studies. The female subjects also perceived tasks as more difficult when slightly dehydrated, although there was no substantive reduction in their cognitive abilities.
In the tests involving the young men, mild dehydration caused some difficulty with mental tasks, particularly in the areas of vigilance and working memory, according to the results of the second UConn study. While the young men also experienced fatigue, tension, and anxiety when mildly dehydrated, adverse changes in mood and symptoms were "substantially greater in females than in males, both at rest and during exercise," according to the study.
"Even mild dehydration that can occur during the course of our ordinary daily activities can degrade how we are feeling – especially for women, who appear to be more susceptible to the adverse effects of low levels of dehydration than men," says Harris Lieberman, one of the studies' co-authors and a research psychologist with the Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine in Natick, Mass. "In both sexes these adverse mood changes may limit the motivation required to engage in even moderate aerobic exercise. Mild dehydration may also interfere with other daily activities, even when there is no physical demand component present."
Why dehydration affects our cognitive abilities and mood needs to be explored with further research. However, according to other research neurons in the brain detect dehydration and signal other parts of the brain regulating mood when dehydration occurs. This process could be part of an ancient warning system protecting humans from more dire consequences, and alerting them to the need for water to survive.
To stay properly hydrated, experts like Armstrong recommend drinking eight, 8-ounce glasses [roughly about 2 liters] of water a day. To check your levels of hydration, monitor the color of your urine—it should be a very pale yellow. Urine that is dark yellow or tan in color indicates greater dehydration. Proper hydration is particularly important for high-risk groups, such as the elderly, people with diabetes, and children.
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