Are you feeling overly tired? Maybe “foggy” or less “alert” or more anxious than usual? Maybe you need a nap, or maybe…you need to drink more water. When we think “dehydration” we think, headaches, thirst, and sometimes dizziness. But did you know that your brain, mental performance and even your mood can be affected by not drinking enough water too?
Role of Water in the Body and Brain
Water is an essential nutrient. It comprises between 45-75% of a person’s body weight, and is critical in several functions such as transporting nutrients, regulating body temperature, lubricating joints and organs, providing structure to cells and tissues, and can help to preserve cardiovascular functioning (Riebl & Davy, 2013). Good hydration can also be helpful for managing your body weight and being able to lose fat (Liska et al., 2019). Water serves an essential role in our physical well-being, but of course if you’re reading about it on my blog, you already know that it serves a critical role in our brain health and cognitive performance as well.
Around 75% of the brain volume is water, so it’s necessary for the very structure of our brain. But water is also necessary for its proper functioning as well. In severe cases, dehydration can result in confusion and delirium (Armstrong et al., 2011). But even as little as a 1% level of dehydration can also cause cognitive impairments. Let’s get our Mrs. Frizzle on and dive into the brain to see how this happens.
For one, our neurotransmitter systems (the chemical signaling molecule for our neurons) tend to act differently when we are dehydrated. These systems can regulate everything from our thinking, our emotions, our memory, our motivation, and even our sleep! It has been shown that serotonin (the “happy chemical”) is decreased when we are dehydrated (Popova et al., 2001), and other neurotransmitters such as dopamine (involved in reward) and acetylcholine (involved in memory) are affected by our water intake, as well (Masento et al., 2014).
Certain hormones are also important in our body’s fluid balance. When we are dehydrated, there is an increase in our levels of cortisol (Masento et al., 2014). If you remember from my stress blog post, cortisol is our stress hormone! This hormone is released as a stress response, which is your body’s way of telling you “drink more water!” When we have higher levels of this stress hormone floating around in the body, we may be less able to remember and to think through things quickly (Masento et al., 2014).
Proper hydration is also necessary for the heart and blood flow, which as you know, is extremely important for brain functions. After drinking a decent amount of water, we experience reduced heart rate because our blood vessels dilate. This increases cerebral blood flow, which makes it easier for oxygen and nutrients to be transported to and used by the brain (Masento et al., 2014). Although a small part of your body, your brain consumes 20% of the oxygen we breathe, and utilizes 100mg of glucose per minute to carry out its basic functions (Bourre, 2006). Without proper blood flow, the brain won’t receive the nutrients it needs to carry out its functions, which can not only result in immediate challenges with mental performance, but also lasting damage to the neurons (Purves et al., 2001).
The Impact of Dehydration on Cognitive Performance
I’ve touched on a few brain challenges that may arise as a result of dehydration already, but here I’ll list them all out.
- Short-term memory
- Psychomotor function
- Concentration
- Degraded mood
- Increased perception of task difficulty
- Alertness
- Fatigue
- Increased reaction time
- Anxiety
These cognitive performance challenges can start to appear when we reach only a state of mild dehydration, one that could occur as a result of just our typical daily activities (Riebel & Davy, 2013)! Luckily for most people, these challenges can be reversed simply by drinking more water. Rehydrating after a period of limiting water intake has been shown to decrease reaction time, improve sustained focus, short-term memory, judgment and decision making, and (best of all?) mood (Riebl & Davy, 2013., Patsalos & Thoma, 2019).
What does this look like in a real world setting? Researchers found that university students who brought a drink of water with them to an exam session had increased performance than the students that did not have water with them (Pawson et al., 2013). So, if you’re feeling overly moody, tired, foggy, having trouble with your memory or your ability to think things through and make proper decisions, or you have an event where your full attention is needed for a lengthy amount of time (so, all of us, all the time…), make sure to drink some water.
How to Drink More Water
Drinking water sounds like an extremely easy task, right? I mean, I’m not asking you to scarf down sardines or brussel sprouts (that’s a blog post topic for another day…). Unfortunately this task is apparently deceptively easy. Approximately 75% of the population is chronically dehydrated. So how can we make this task even simpler, to make sure our bodies and brains are getting enough of the water it needs? Here are a few tips to ensure you’re getting at least 8 cups per day.
- Consume Caffeine Carefully: The good news for all my coffee lovers out there is that the popular myth (you heard that right…MYTH) that coffee causes dehydration isn’t actually the whole truth. Coffee consumption can actually be considered a source of fluid that improves hydration status (Riebl & Davy, 2013), in appropriate amounts. 1-2 cups per day of coffee or caffeinated tea can be counted towards your total water consumption. But be careful, anything more than that might actually have the reverse effect, acting as a diuretic thus contributing to dehydration.
- Watch Your Alcohol: Speaking of diuretics, alcohol is one of the worst offenders. Ever wonder why you pee so much when you’re drinking alcohol (all my women who have ever had to wait in a bar bathroom line know this pain!)? It’s because alcohol promotes water loss through urine. When you’re enjoying a few cold ones, make sure to alternate with a glass of water (I apologize in advance for the increased bathroom breaks..)
- Carry A Water Bottle: people who carry around a water bottle have an increased chance at staying hydrated. Make sure to bring one with you everywhere you go! Bonus points if it’s a reusable metal or glass bottle!
- Use Water as an Appetizer: I use meal time as my cue to drink some water. While I’m making my dinner, or before going to grab my lunch from the fridge, I take some time to enjoy a glass or so of water. Meal time, when you’re breaking your concentration anyway, serves as a great reminder to drink up!
- Enjoy Other Water Sources: Not a fan of water? You’re not alone. The “boring” taste can make it hard to sip on daily. If this is you, try infusing your water with lemons, lime, strawberries, or other delicious fruits. You can also drink seltzer water, which makes hydrating a little more fun (I mean, who doesn’t love bubbles?).
Although not a nutrient we typically think of when it comes to brain health and mental performance, water is crucial in our ability to perform at our Peak. Some of the symptoms you probably attributed to a bad night’s sleep or a frustrating coworker might actually be solved by a simple trip to the water cooler. The average person requires at least 8 cups of water per day, and even more when it’s hot or you’re active and sweating. If you find it hard to get your daily 8 cups, try some of these tips out! Let me know which one you like the most in the comments below.
References
Armstrong, L. E., Ganio, M. S., Casa, D. J., Lee, E. C., McDermott, B. P., Klau, J. F., Jimenez, L., le Bellego, L., Chevillotte, E., & Lieberman, H. R. (2011). Mild Dehydration Affects Mood in Healthy Young Women. The Journal of Nutrition, 142(2), 382–388. https://doi.org/10.3945/jn.111.142000
Bourre J. M. (2006). Effects of nutrients (in food) on the structure and function of the nervous system: update on dietary requirements for brain. Part 2 : macronutrients. The journal of nutrition, health & aging, 10(5), 386–399.
Liska, D., Mah, E., Brisbois, T., Barrios, P. L., Baker, L. B., & Spriet, L. L. (2019). Narrative Review of Hydration and Selected Health Outcomes in the General Population. Nutrients, 11(1), 70. https://doi.org/10.3390/nu11010070
Masento, N., Golightly, M., Field, D., Butler, L., & Van Reekum, C. (2014). Effects of hydration status on cognitive performance and mood. British Journal of Nutrition, 111(10), 1841-1852. doi:10.1017/S0007114513004455
Patsalos, O. C., & Thoma, V. (2019). Water supplementation after dehydration improves judgment and decision-making performance. Psychological Research, 84(5), 1223–1234. https://doi.org/10.1007/s00426-018-1136-y
Pawson, C, Gardner, MR, Doherty, S, et al. (2013) Drink availability is associated with enhanced examination performance in adults. Psychol Teach Rev 19, 57–67
Popova, N. K., Ivanova, L. N., Amstislavskaya, T. G., Melidi, N. N., Naumenko, K. S., Maslova, L. N., & Bulygina, V. V. (2001). Brain serotonin metabolism during water deprivation and hydration in rats. Neuroscience and Behavioral Physiology, 31(3), 327–332. https://doi.org/10.1023/a:1010346904526
Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. The Blood Supply of the Brain and Spinal Cord. Available from: https://www.ncbi.nlm.nih.gov/books/NBK11042/
Riebl, S. K., & Davy, B. M. (2013). The Hydration Equation. ACSM’S Health & Fitness Journal, 17(6), 21–28. https://doi.org/10.1249/fit.0b013e3182a9570f