Years of research have found that when we’re parched, we have more difficulty keeping our attention focused. Dehydration can impair short-term memory function and the recall of long-term memory. The ability to perform mental arithmetic, like calculating whether or not you’ll be late for work if you hit snooze for another 15 minutes, is compromised when your fluids are low.
To put the water requirements in perspective: The average adult brain is 1.3 to 1.4kg and is approx 2% (obviously varies) of the overall weight of the adult human. The brain is 70-80% water and at least two more significant fluids which are reliant upon the availability of water indirectly are present: blood @ 150 ml (10%) and cerebrospinal fluid (CSF) @ 150 ml (10%) (from Rengachary, S.S. and Ellenbogen, R.G., editors, Principles of Neurosurgery, Edinburgh: Elsevier Mosby, 2005). Everyone’s metabolism varies, but if your body is consuming water elsewhere, then the brain will be deprived as the body shares out what water there is to the essential organs. If you are noticing the signs of mild or acute dehydration, then the rest of the body and brain already has been deprived in some way.
Drinking water for your brain function should not be confused with Hydrocephalus , which was was once known as “water on the brain,” and the “water” was actually cerebrospinal fluid (CSF) — a clear fluid that surrounds the brain and spinal cord.