Cranky or sluggish today? Even mild dehydration can alter our moods and energy.
Most people only think about drinking water when they are thirsty; but by then it may already be too late, according to two studies recently conducted at the University of Connecticut’s Human Performance Laboratory. Mild dehydration is defined as an approximately 1.5 percent loss in normal water volume in the body.
The test results affirm the importance of staying properly hydrated at all times and not just during exercise, extreme heat, or exertion, says Lawrence E. Armstrong, one of the studies’ lead scientists and a professor of physiology in UConn’s Neag School of Education.
“Our thirst sensation doesn’t really appear until we are 1 percent or 2 percent dehydrated. By then dehydration is already setting in and starting to impact how our mind and body perform,” says Armstrong, an international expert on hydration who has conducted research in the field for more than 20 years. “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 percent of their body weight as water when they compete.”
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Separate groups of young women and men were tested.
In the tests involving the young women, mild dehydration caused headaches, fatigue, and difficulty concentrating, according to one of the studies, which appears in the February issue of The Journal of Nutrition. 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. The men’s study was published in the British Journal of Nutrition in November 2011.
In order to stay properly hydrated, experts like Armstrong recommend that individuals drink eight, 8-ounce glasses of water a day, which is approximately equivalent to about 2 liters of water. People can check their hydration status by monitoring the color of their urine. Urine should be a very pale yellow in individuals who are properly hydrated. 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.
J Nutr. 2012 Feb;142(2):382-8. Epub 2011 Dec 21. “Mild dehydration affects mood in healthy young women.” Armstrong LE, Ganio MS, Casa DJ, Lee EC, McDermott BP, Klau JF, Jimenez L, Le Bellego L, Chevillotte E, Lieberman HR. University of Connecticut, Human Performance Laboratory, Storrs, CT.
Br J Nutr. 2011 Nov;106(10):1535-43. Epub 2011 Jun 7. “Mild dehydration impairs cognitive performance and mood of men.” Ganio MS, Armstrong LE, Casa DJ, McDermott BP, Lee EC, Yamamoto LM, Marzano S, Lopez RM, Jimenez L, Le Bellego L, Chevillotte E, Lieberman HR. Texas Health Presbyterian Hospital, Institute for Exercise and Environmental Medicine, Dallas, TX 75231, USA.