Dehydration causes your brain SWELL, making it harder for you to complete everyday tasks

Did you know that dehydration can cause both physical and mental changes to the body?

Researchers from the Georgia Institute of Technology have found that dehydration actually causes part of your brain to swell and negatively impacts cognitive function. The study, published in the journal Psychological Reports, investigated the effects of dehydration on the human body when coupled with heat and physical activity.

Dehydration is a deficiency of water in the body and occurs when the body’s fluid loss is greater than its fluid intake. Normal body functions such as urinating, perspiring, crying, and even breathing all contribute to fluid loss. The symptoms of dehydration include bad breath, dry skin, headaches, increased thirst, dry mouth, tiredness and dizziness.

According to Mindy Millard-Stafford, the study’s principal investigator and a professor at Georgia Tech’s School of Biological Sciences, the researchers wanted to “tease out whether exercise and heat stress alone have an impact on your cognitive function and study the effect of dehydration on top of that.” (Related: Mild dehydration can have serious effects on health.)

For the study, the researchers observed 13 volunteer participants. The participants were subjected to monotonous repetitive tasks, such as pushing a button whenever a yellow square appeared on a monitor. The yellow square would appear intermittently, switching between regular and random intervals. The participants performed this task for 20 minutes straight to test their responsiveness. The researchers made the test subjects repeat this task on three separate occasions. Once after relaxing and staying hydrated, then once after physical exertion, heat exposure and staying hydrated, and finally once after physical exertion, heat exposure and going without hydration. The participants completed the tasks in air-conditioned rooms and after a break from strenuous activity.

The researchers found that even after just relaxing, the performance of the participants diminished over time. Additionally, Millard-Stafford says the researchers found a “two-step decline.” Even without being dehydrated, the heat and physical exertion alone had a negative impact on the test subjects’ performance. However, with the fluid loss, the effect was doubled. Dehydration led most of the test subjects to make even more mistakes.

Brain swelling and neural firing

The human brain contains a network of cavities called ventricles. These ventricles are filled with fluid. During the study, the researchers used functional magnetic resonance imaging (fMRI) to observe the ventricles of the participants. What they found was that when participants exercised, sweated and drank water, the ventricles in the center of their brains contracted. But when the participants exercised, sweated and did not drink water, the ventricles had the opposite reaction. They expanded.

However, the ventricle expansion in the dehydrated participants may not have had much to do with their declining task performance.

“The structural changes were remarkably consistent across individuals,” Millard-Stafford added. “But performance differences in the tasks could not be explained by changes in the size of those brain areas.”

The researchers also observed changes in neural firing patterns during dehydration.

Based on the results, the researchers concluded that dehydration can cause part of the brain to swell and can make it more difficult to carry out monotonous tasks that required attention to detail.

How much water is enough

Staying hydrated is important but how do you know if your water intake is too little or too much? Millard-Stafford warns that overhydration is just as bad. The human body must have just the right balance between water and blood sodium. Too much water and too little blood sodium can lead to a dangerous condition known as hyponatremia or water intoxication.

There is the common age-old advice of drinking eight glasses of water a day, but this standard doesn’t adequately suit all body types. According to the National Academies of Sciences, Engineering and Medicine, the recommended daily fluid intake for the average healthy adult living in a temperate climate is around 3.7  liters for men and 2.7 liters for women.

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