A study shows that even a very slight decrease in body water content (less than 1%) is already enough to affect cognitive functions such as memory or attention and even affects mood. A glass of water on hand is good for the body and the brain.
Dehydration is known to affect physical and cognitive performance, but it is generally considered that it must correspond to a water loss of at least 1 to 2% of body weight to have measurable consequences. However, a more specific study reports that even small fluctuations already have repercussions on cognitive functions.
The subjects were exposed to a temperature of 30°C for 4 hours. During this period, some were able to consume 300 ml of water, others not, and this, in a randomized way. Changes in body composition, urinary tract, body temperature and thirst were tracked. The authors also measured, on three different occasions, episodic memory, focused attention, mood and perceived task difficulty.
Lack of water: memory, attention and mood disorders
The results show that water consumption significantly improved memory and focused attention. Effects which, in the short term, are associated with thirst. In the longer term, greater water loss (average loss of 0.72% of body weight) is associated with poorer memory and poorer attention. After 90 minutes, increased thirst is associated with a decline in subjective energy and feelings of anxiety and depression. These effects were reduced by water intake. At 180 minutes, the subjects found the tests easier to perform if they had drunk water. The study concludes that water consumption is beneficial for cognitive functions in the face of water losses that easily occur on a daily basis.
Benton D et al: Minor degree of hypohydration adversely influences cognition: a mediator analysis Am J Clin Nutr