Even mild dehydration can alter a person's mood, energy level and ability to think clearly, but the effect might be more acute in women, U.S. researchers said.

Lawrence E. Armstrong, a professor of physiology at the University of Connecticut, said two studies affirm the importance of staying properly hydrated at all times and not just during exercise, extreme heat or exertion.

For the purposes of the study, mild dehydration was defined as an approximately 1.5 percent loss in normal water volume in the body, Armstrong said.

The researchers showed it didn't matter whether a person had just walked for 40 minutes on a treadmill or was sitting at rest -- the adverse effects from mild dehydration were the same.

The researchers examined two groups of healthy, active people -- one with 25 women,

average age 23, and the other with 26 men, average age  20. None were high-performance athletes and nine were sedentary, and all typically exercised for 30 to 60 minutes per day. Each took part in three evaluations that were separated by 28 days.

One study, published in February's The Journal of Nutrition, found in the tests of young women, mild dehydration caused headaches, fatigue and difficulty concentrating.

The second study published last November in the British Journal of Nutrition found in the men mild dehydration caused some difficulty with mental tasks, particularly vigilance and working memory -- but the adverse changes in mood and symptoms were "substantially greater in females than in males, both at rest and during exercise. (UPI)

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