The Cognitive Effects 

of Proper Hydration 
The Cognitive Effects 

of Proper Hydration 

Most people have a fairly good understanding of how 

dehydration affects the body, but not everyone fully 

understands how it affects the mind. 

This is a serious issue. While the ideal fluid intake 

varies from person to person, a five-year study of 

over 15,000 Americans between the ages of 20 and 

50 found that 43% of men and 41% of women failed 

to meet the daily intake recommendations from the 

U.S. Institute of Medicine — and that they drank less 

as they got older. 

In this article, we’re going to look specifically at the 

cognitive impact of proper hydration — how it affects 

the brain, cognitive processes, and mood. 
 

Why the Brain Needs Water 

The human body is anywhere from 45 to 75 percent water, so it needs proper hydration 

to function optimally. That’s particularly important for the brain, which is composed of 

73 percent water. 

To operate, the brain cells need to maintain a balance 

between water and a number of other different elements — 

and when the body loses too much water, it disrupts that 

delicate balance. As a result, the brain cells become less 

efficient. The brain, which 

is composed of 73 

So, how does this affect someone at work or in percent water. 

day-to-day life? 

It can manifest in a few different ways, all of which are signs and symptoms that we 

generally associate with dehydration: 

• Difficulty focusing 

• Impaired short-term memory 

• Difficulty recalling long-term memories 

• Impaired ability to perform mental 

arithmetic (like making simple calculations) 

Not only are these unpleasant, in the workplace, they can also lead to a higher likelihood 

of mistakes - and accidents. 
 

 

The Link Between Cognition and Hydration 

Various studies have demonstrated the link between good cognitive function and proper 

hydration. The affected functions can include: 

• Concentration or attentiveness 

• Concept learning 

• Critical thinking 

• Memory 

• Reaction time 

• Accuracy during complex tasks 

In one study examining the impact of hydration on visual sustained attention, 

researchers found that the group that consumed the most water (330 mL) performed 

best on the visual attention test, while those in the no-water group performed the 

worst. Another study replicated this research while minimizing variability in baseline 

hydration levels. It found that young adults who were given 200 ml of water saw 

increased performance from the baseline in a sustained attention task that involved 

searching for a specific letter within a grid. 

Researchers have also found that short-term memory improves after fluid consumption. 

In three different studies (found here, here, and here), subjects’ performance on 

memory-related tests — such as recalling a list of objects — improved after water 

consumption compared with their no-water performance. And while these three studies 

all looked at school-age children, it’s likely that the findings would hold true for adults 

as well. 

While more in-depth research is needed regarding how hydration levels affect reaction 

time, research published in Frontiers of Human Neuroscience notes performance 

differences in reaction time between individuals who were thirsty and those who were 

not. Non-thirsty individuals showed similar performance in a battery of tests, while 
 

those who were thirsty and did not have water performed significantly worse and had 

slower reaction times. 

In other words, a properly hydrated workforce is a better workforce, no matter what 

kind of work they’re doing. In hot environments that involve physical labor, they’re also 

a much safer workforce. 

How Hydration Affects Mood 

There are a variety of studies that note the link between dehydration and mood 

disturbances, but there are also some that have found a positive link between fluid 

consumption and self-reported mood. 

In one study reported in the journal Appetite, individuals reported feeling calmer and 

more alert after consuming water. The results of this study were verified by a number of 

other studies that reported similar findings. 

Researchers have also found that tension, depression, and confusion scores decrease 

as water intake increases. In contrast, they found that low water consumption tends to 

lead to worse moods, as well as headaches, confusion, and tiredness. 

When you consider that dehydration affects the flow of oxygen to the brain and causes 

the heart to work harder to pump oxygen to the organs, it’s not surprising that being 

under-hydrated - not to mention dehydrated - can make you feel groggy and lacking 

in energy. That helps explain why when you’re feeling this way and then consume a 

glass or two of water or a an electrolyte replenishment beverage, you “perk up” and 

immediately start feeling more alert. 
 

Hydrating to Fuel Your Brain 

Unlike other areas of the body, the brain has no way 

to store water. For this reason, it’s important to ensure 

you’re hydrating adequately throughout the day. 

The general guideline to follow is one cup of water 

for every 20 pounds of body weight. However, there 

are a number of factors that influence hydration 

requirements, including medications, temperature and 

humidity levels, and physical activity or exertion. The 

more fluid you lose, whether it’s from sweating under 

protective equipment or simply from breathing, the 

more you need to take in. 

It’s important to remember that all fluids count towards 

keeping you hydrated. Water or electrolyte 

replenishment beverages like Sqwincher are 

an excellent choice, but coffee and even 

food (especially those with high water 

content) work, too. 

If you’re rarely feeling thirsty, making 

regular (but not too regular) trips to 

the bathroom, and your urine is almost 

colorless, these are all good signs that 

you’re likely well hydrated and helping to 

keep your brain at peak performance.