Dehydration can exacerbate mental fatigue

Dehydration can cause flu-like symptoms during exercise, is one of the main reasons why alcohol is so bad for you, is one of the only risk factors of using steam rooms, and could be the reason why it is so hard to lose weight.

Re-hydration, though, is one of the best ways to increase energy (and even clears out clear out mucus passages).

Dehydration does more than make you thirsty. Your body needs water to eliminate toxins and transport important nutrients like oxygen throughout its entire system. Could your lack of brain power be caused by a lack of water?

aqua drinking water
Taylor and Francis Online proved that a small 2% drop in hydration levels was enough to hamper mental performance. 11 People were subjected to dehydration by restricting water intake while exercising in warm conditions to induce sweat. Hydration levels were constantly measured while mental tests were conducted regularly to measure what dehydration level started to impact brain function. The results were staggering: After a meager 2% loss in overall water weight, all participants scored less than their pre-determined averages on tests that measured mathematics ability and short-term memory.

Moral of the story: Your brain starts to lose its ability to function – even at low levels of dehydration.

As we all know, alcohol reduces cognitive function. It does this by dehydrating you as your body uses a lot of to water to expel the alcohol from your blood stream. Severe dehydration is what causes a hangover the next morning. Alcohol consumption might show us the extreme effects of dehydration on mental function, but there are studies that show that even mild dehydration impairs our mental ability. A 2015 study conducted at Loughborough University of England concluded that we shouldn’t even be driving while dehydrated. Test subjects were dehydrated and put through simulated driving tests. They made many more mistakes when their bodies needed water, like using brakes too late or failing to stay within their respective lanes. You can find that study here.

So how exactly does dehydration affect mental performance?

1) Liver health

Dehydration impairs your liver’s ability to eliminate toxins efficiently. This is why people who drink a lot of alcohol are at risk of permanent liver damage, called cirrhosis. Impaired liver function actually has a lot to do with mental health. How so? Because your liver is responsible for converting and maintaining optimum glucose levels – and glucose is your brain’s primary energy source. When your liver isn’t happy, your brain won’t be.

2) Cortisol

Cortisol is a stress hormone that your brain releases when it experiences stress. Historically, cortisol helped humans survive by slowing down normal bodily functions and prioritizing the production of quick, easy-to-use energy that could help us escape dangerous situations like predators or clan wars. The functions that are slowed down include digestion, recovery, and (you guessed it) mental performance. Muscles are tensed via cortisol production in an attempt to prepare for physical exertion. This is why stress causes knots in muscle tissue. Dehydration is seen by the body as a stress, and this explains why people who are dehydrated are more susceptible to mental stress. In the wild, we wouldn’t have access to water when we were in stressful situations, and we would be able to relax and re-hydrate when we have escaped the stressful situation. This might explain why people report feeling more relaxed after they are properly hydrated.

3) Blood flow

Our bodies need water to eliminate toxins from our organs and replenish them with much needed nutrients. When we are dehydrated, our blood has less carrying capacity to deliver these nutrients or eliminate toxic by-products. This is why people with low blood pressure feel weak. Ironically, this is also why high blood pressure is also so dangerous: Our bodies get so clogged up that our systems can’t get the blood flow that they depend on. Our brains need blood flow just as much (if not more) than our other organs in order to function properly. Sufficient blood flow is needed by the brain to eliminate out-of-use chemicals and create new ones. This is why drinking a big glass of water wakes you up so well in the morning: Your brain can eliminate sleep hormones like melatonin and let the pancreas start producing wake-full hormones like glucagon. Glucagon is a peptide hormone that increases glucose and fatty acid levels, which the body uses for energy.

4) De-sensitivity to dehydration

Your conscious mind only becomes aware of dehydration when your hydration levels fall at a fast rate. If you stay within a mild state of dehydration for a long period of time, you body starts to accept this as normal. This means that you could be dehydrated without ever feeling thirsty. Your body accepts that state as normal, but adjusts by limiting internal functions in order to survive.
Also, your conscious mind can only handle one thing at a time. Have you ever worked so hard that you forgot to eat? Mental stimulation does not take away hunger – it only takes your focus away from what your body needs. The same thing happens with dehydration.

Dehydration causes a negative cycle of over sensitivity to stress (as explained in point 2 above), which makes your brain focus more energy on a particular task than what it actually needs to. Since simple tasks require more concentration, your brain is too preoccupied by these tasks to realize that it needs more water.

5) Dehydration causes unhealthy cravings

Dehydration causes a sense of need that your body tries to satisfy. Unfortunately, thanks to unnatural foods and artificial ingredients, your body gets confused and will send out a false craving signal in order to satisfy that need. Think about beef flavored potato chips: They taste salty and are flavored to taste like beef, making our minds think that we are eating a protein-based food when they are actually carb-based. The same false-craving can happen when we are dehydrated. Some people crave nicotine from cigarettes, alcohol or sugary drinks when what their bodies actually need is water. This explains why drinking a glass of water is so effective at postponing cigarette cravings: You are satisfying your body’s need for hydration and allowing it to detoxify itself with that water – helping it to gradually overcome substance withdrawal.
The water-before-soda challenge is another example of how our bodies need one substance but crave another. Try this out: Every time you crave a soda drink, down a glass of water with the promise that you will still have that soda if the craving is still there. More than half the time, you won’t crave that soda anymore. This is proven to be an effective way of drastically decreasing the amount of soda drinks consumed. It is often not the soda or the flavors that we crave, but our body’s desperate outcry for hydration.
Other examples of false-cravings include the fact that people often crave high fat foods when they have under slept, but crave more sleep when they have overslept.
If I have convinced you that your body might need more water than you previously thought, I’ve done my job. Try sipping on pure water throughout the day and take a mental note about how you feel, how productive you are and whether or not your overall quality of life has improved. I look forward to hearing your thoughts on this in the comments.

As always feel free to like, reblog, share, link to or comment on my work. Have a great day!


  1. Love it Saguren! I knew hydration was important for bodily function and weight management, but never knew how tied it was to mental health. I’m so glad I made getting back to the basics (like drinking water and eating whole foods) part of my plan to get back in shape. As always, thanks for sharing.

    Liked by 2 people

  2. Great topic Saguren, I know people that work all day and hardly drink any water, except at lunch. I get thirsty just knowing that I don’t have a glass by my side – even at night – I have a big glass of water on my nightstand, just in case I get thirsty. Lord knows I hate getting out of bed… LOL 🙂 thank you again Saguren!

    Liked by 2 people

  3. Recently my doctor said some tests showed I was near dehydration. I still don’t understand how when I drink 64oz of water a day. But I do have several symptoms you listed. Thank you for confirming what I was told.

    Liked by 1 person

    1. I am glad that the article helped you. Are you drinking it all at once or throughout the day? Also, how is your blood pressure? I have low blood pressure and therefore need to add a pinch of salt to my water so that my body doesn’t pee it out as soon as I drink it.

      Liked by 1 person

      1. I drink it throughout the day, but I also drink several cups of coffee. Maybe that effects it. My blood pressure is normal and salt level is low (except I sadly almost everything so I was amazed)

        Liked by 1 person

      2. Have you tried reducing your coffee intake? Are maybe replacing coffee with green tea to see if you feel better? Imagine if a simple switch or reduction is all that you need to have more energy every day.

        Liked by 1 person

      3. I’m intrigued to see how it works. Please please provide feedback about your energy levels when you try it. Testimonials like that give me a good idea of what works and what doesn’t. I can’t do caffeine experiments on myself because I don’t drink much caffeine. I personally avoid it so that my body learns to regulate it’s own energy levels.

        Liked by 1 person

      4. Can you try swapping it out with green tea and seeing what happens? There is caffeine in green tea, but not as much so maybe it will balance your energy systems.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s