One of the stranger things I’m known for among my friends is that I never get thirsty. Not after exercising, not even after a sauna. Unless I actively remind myself, I simply forget to drink.
It’s only in the extraordinarily hot UK weather of late that I’ve begun to wonder whether this biological blind spot is contributing to my recent brain fog and general lack of cognitive sparkle. Is dehydration to blame, and if so, how much should I drink to keep my brain working at its best? Water is, needless to say, essential for the brain.
It helps neurons transmit electrical impulses, delivers vital nutrients to power cells and flushes out toxins while we sleep, among other things. Unfortunately, pinning down its exact effect on cognition is challenging, partly because most studies on hydration and brain function are fairly small. Nevertheless, together they offer some intriguing clues.
The ultimate guide to hydration and what you really should be drinking For instance, in one study, 29 adults completed a bunch of cognitive tests on two occasions, each following 12 hours without food or water. Before one testing session, they were offered a 500-millilitre bottle of water and were told they could drink as much as they wanted. People scored better in tests of judgement and decision-making that required them to suppress a quick gut feeling and instead engage slower, more reflective thinking after they had drunk water.
This result held regardless of how thirsty or motivated they felt. This was the first study to suggest that water might influence this ability, known as “cognitive reflection”, but the study was small, so it is difficult to say why. One possibility, suggest the researchers, is that dehydration reduces blood flow to the anterior cingulate cortex, which is a brain region we use to inhibit actions.
Dehydration can also increase blood levels of cortisol, a stress hormone that has been shown to interfere with decision-making. In other studies, dehydration wasn’t found to have a significant impact on cognitive performance, but participants reported that the tasks felt more effortful when they were dehydrated. To investigate further, Matthew Kempton at Kings College London and his colleagues asked 10 students to spend 90 minutes cycling on a stationary bike – once wearing regular exercise wear and another time wearing a black bin liner next to their skin, followed by a chemical warfare protective suit and finally a tracksuit.
Extract — continue reading at the source.
