Your brain literally shrinks in volume when it doesn't get enough water, a growing body of research has shown.
When we're dehydrated, moodiness, decreased energy levels and perceiving tasks to be more difficult can come with the brain-shrink.
In fact, a study on teenagers by the Centre for Neuroimaging Sciences in London found that when subjects were dehydrated, their brains had to work harder than when they weren't dehydrated. The findings suggest that prolonged states of reduced water intake may adversely impact executive functions such as planning and visual-spatial processing.
"The brain is extremely sensitive to even small changes in the amounts of ions like sodium and potassium found in your body's fluids," scientist and researcher Harris Lieberman explained to Shape magazine, adding that even mild dehydration can be detrimental to the proper functioning of your brain.
"And don't fall into the trap of thinking that grabbing a mug of coffee or an energy drink is what you need," warned Tony Marchesini, managing director of H2O International SA. "Nothing comes close to pure water for ideal brain health."
Six to eight glasses of water per day are recommended. "Remember, however, that much of this water could be obtained from water-rich foods you consume," dietician Ashley Gibbon previously told HuffPost — "especially fruits and vegetables such as watermelon, tomatoes and celery, all of which are more than 90 percent water."