Even Mild Dehydration May Cause Emotional, Physical Problems

Denise Mann

January 20, 2012

January 20, 2012 — Even mild dehydration may affect our moods and ability to concentrate.

In a new study of 25 healthy women, mild dehydration dampened moods, increased fatigue, and led to headaches.

The women in the study were aged 23, on average. They were neither athletes nor couch potatoes. Women participated in three experiments separated by 28 days. In two of these, dehydration was induced via walking on a treadmill with or without a diuretic pill. These pills encourage urination, and can lead to dehydration.

The women were given a battery of tests measuring their concentration, memory, and mood when they were dehydrated and when they were not.

Overall, women’s mental ability was not affected by mild dehydration. But they did have an increase in perception of task difficulty and lower concentration.

But “women were more fatigued and this was true during mild exercise and when sitting at a computer,” says researcher Lawrence E. Armstrong, PhD. He is a professor of environmental and exercise physiology at the University of Connecticut's Human Performance Laboratory in Storrs, Conn.

The findings appear in The Journal of Nutrition.

Armstrong and colleagues previously looked at the effects of mild dehydration in men. Although men did experience some subtle mental difficulties when dehydrated, the risks were pretty similar between the sexes.

The message is clear, he says: “We should focus on hydration and continue to drink during meals and when we are not at meals.”

Avoid Dehydration: Drink More Water

You are often already dehydrated once you become thirsty, but subtle cues like a headache and/or fatigue can be your body’s way of telling you to drink more water, Armstrong says.

The new study should serve as a reminder for healthy, young women who frequently exercise to drink water, says Robert Glatter, MD. He is an emergency medicine physician at Lenox Hill Hospital in New York City.

“Consume moderate quantities of water both during and after exercise in order to avoid mild dehydration, which may lead to headaches, fatigue, and difficulty concentrating,” he says in an email.  “Just a small change in state of hydration was enough to affect mood, ability to concentrate, and lead to development of headaches.”

It is unclear if these findings apply to other populations at risk for dehydration, such as the elderly, people with diabetes, and children, Glatter says.

The best way to avoid becoming dehydrated is to drink an adequate amount of water. 

Olveen Carrasquillo, MD, agrees. He is the chief of the division of general internal medicine at University of Miami Miller School of Medicine.

So, how much water do we need? “For most healthy people, six to eight glasses of 8 ounces of water a day is what we recommend,” he says. The effects of even mild dehydration are likely to be even more pronounced in high-risk groups, such as the elderly and young children.

Knowing the signs of dehydration can also keep you out of the danger zone. Another sign is dark urine. “Your urine should be a light yellow color,” Glatter tells WebMD.

Not everyone needs to drink this much water. “People with congestive heart failure and people with certain kinds of kidney disease may want to limit their fluid intake, and should talk to their doctor about how much water they should drink,” he says.


Armstrong L.E. Journal of Nutrition, 2102.

Lawrence E. Armstrong, PhD, professor, environmental and exercise physiology, Human Performance Laboratory, University of Connecticut, Storrs, Conn.

Olveen Carrasquillo, MD, chief, general internal medicine, University of Miami Miller School of Medicine, Miami.

Robert Glatter, MD, emergency medicine physician, Lenox Hill Hospital, New York City.


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