(RxWiki News) If you're waiting until you feel thirsty before drinking water, then you're waiting too long. And without proper hydration, you're likely to feel moody, anxious and unable to concentrate.
Whether you're exercising or chilling in front of TV, your body needs hydration to prevent problems with memory, concentration, anxiety, headaches and range of other mental difficulties, according to recent studies.
"Drink plenty of water each day."
Both studies were conducted by the same team of researchers. One was led by Lawrence Armstrong, a physiology professor at the University of Connecticut's department of Kinesiology, and the other was led by Matthew Ganio of the Institute for Exercise and Environmental Medicine at Texas Health Presbyterian Hospital in Dallas.
Mild dehydration means having an approximately 1.5 percent less water in the body than a person normally should have. The best way to stay hydrated is to drink a total of about 2 liters of water daily, equivalent to about eight 8-oz glasses.
One easy indicator of how well you're hydrated is to look at how yellow your urine is: very pale yellow indicates good hydration but dark yellow or tan means you need to drink more.
The researchers investigated two groups as part of two different studies: a group of 25 women with an average age of 23 and a group of 26 men with an average age of 20.
All the participants were healthy and active and got about 30 to 60 minutes of exercise each day, though none were high-performance athletes.
Researchers evaluated the participants three times over three months by causing intentional mild dehydration and then giving them a range of cognitive tests.
The tests evaluated the participants' vigilance, concentration, reaction time, learning, memory and reasoning skills. The researchers compared the participants' results when they were slightly dehydrated to when their bodies had an adequate amount of water.
All the men and women went to bed the night before the tests fully hydrated but walked a treadmill the day of the test to induce dehydration.
The dehydrated women experienced headaches, fatigue and difficulty concentrating, and they believed the cognitive tests were harder when they were dehydrated even though they performed just as well as while hydrated.
The men with dehydration had trouble with staying alert and using their memory. They also experienced fatigue, tension and anxiety while dehydrated.
The women, however, suffered more in terms of their mood and overall dehydration symptoms, according to the researchers' results, though they're not sure why.
"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," said co-author Harris Lieberman, a research psychologist with the Military Nutrition Division at the U.S. Army Research Institute of Environmental Medicine.
"In both sexes these adverse mood changes may limit the motivation required to engage in even moderate aerobic exercise," Lieberman said. "Mild dehydration may also interfere with other daily activities, even when there is no physical demand component present."
Groups with more vulnerable health, such as children, the elderly and people with chronic health problems such as diabetes, should especially ensure they are getting enough water each day.
But often it's people sitting at their desks all day who forget to keep swigging the water - even though they need it just as much as a marathon runner.
"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," said Armstrong.
"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," he said.
The study of the dehydrated women, led by Armstrong appears in the February issue of The Journal of Nutrition, and the study of the men, led by Ganio, appeared in the November 2011 issue of the British Journal of Nutrition.
Both studies were funded by Danone Research of France and supported by the U.S. Army Research Institute of Environmental Medicine, University of Arkansas and Texas Health Presbyterian Hospital's Institute for Exercise and Environmental Medicine in Dallas.
Armstrong is a Danone Research Scientific Advisory Board member, and both Armstrong and Lieberman are consultants for Danone Research. Three other authors are Danone employees, and the remaining authors declared no competing interests.