Your brain is literally made up of water (75% to be exact!), so it needs fluids in order to work properly. “[Water is] going to help keep your blood pressure normalized; it’s going to help flush out [waste] from your cells; it keeps your cells metabolically active and healthy,” Willeumier adds, all of which are important functions for brain health.
Not to mention, water is crucial for memory and mental clarity: Willeumier explains that even if you have a 1 to 2% drop in hydration, you can start to have symptoms associated with brain fog, like fatigue, headache, and poor concentration. Another study shows that when a group of young, healthy women restricted their water intake to no more than 6 ounces in one day, they performed worse on cognitive tests that required visual and working memory; after they drank enough water and repeated the tests, their executive function went back to baseline.
The bottom line? Dehydration (even a mild drop) can sabotage your mental game and make you feel a bit under the weather. That’s why, Willeumier notes, “One of the first things I do when I teach people about taking care of their brain health is to make sure they are drinking their daily requirement [of water].”