I expect you know how important water is to our bodies. But I wonder if you know just how important it is.

The brain is made up of nearly 80% water. Your brain can’t function properly when it’s not sufficiently hydrated. An average person needs to drink around 2 L of water a day. (You need to check what’s appropriate for you though. For example, if you are on medication for high blood pressure.)

Only one or 2% dehydration causes critical shrinkage of the brain, impairing neuromuscular coordination, concentration and thinking. It can alter the concentration of electrolytes, such as sodium potassium and chloride. That also has a negative effect on your brain’s functioning.

Your brain can’t store water. So you really must drink even when you’re not thirsty. And by the way, as we get older, we tend to lose our sense of thirst, so count the number of glasses you drink. You may find it’s fewer than you think.

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