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Cognitive benefits of drinking water: stay hydrated, keep your mind sharp
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“Stay hydrated” is a universal health message that applies to people across all life stages. Adequate fluid intake is essential for the body to function properly, as water makes up 60-70% of your body and 75-80% of your brain[1 Trusted Source 2019 - Frontiers in Neurology Systematic and meta-analysis A Single-Scan, Rapid Whole-Brain Protocol for Quantitative Water Content Mapping With Neurobiological Implications ] . There is a strong connection between hydration and brain function; keeping your brain well-hydrated supports optimal performance. Even mild dehydration—losing just 1-2% of body water—can affect focus and temporarily impair memory[2 Trusted Source 2021 - Journal of the American College of Nutrition Systematic and meta-analysis The Validity of Urine Color as a Hydration Biomarker within the General Adult Population and Athletes: A Systematic Review ] . When dehydration exceeds 2%, cognitive functions can be severely impacted. The good news is that rehydration is quick and straightforward. Discover the brain benefits of drinking water.
What can dehydration do to your brain?
Dehydration impacts cognitive performance, particularly in areas like attention and memory. Imagine, a hot summer day with temperatures around 33°C and you are working out in the heat for 50 minutes. Lack of adequate hydration can easily dehydrate you, and you can lose up to 2% of your body weight in water in this case[3 Trusted Source 2018 - BMC Sports Science, Medicine and Rehabilitatio Human study Effects of heat stress and dehydration on cognitive function in elite female field hockey players ] . This can lead to physical and cognitive changes in the brain like brain fog. Dehydration during longer periods increases the risk of cognitive decline like dementia and mood disorders like depression. Let’s take a look at why drinking water is important.
What happens to your body when you start drinking more water?
When you increase your water intake all your bodily functions normalise. Does water help brain function? It does - enough water improves your cognitive function and also supports your physical performance and mood. Have a closer look at how water and brain function are connected.
What are the 5 most important reasons to drink water?
Besides improved brain function, physical performance and enhanced mood, drinking enough water also supports vital bodily function and promotes brain health by allowing your body to maintain a ratio of water that is needed for your body to function properly.
1 Better attention and memory
Upon mild dehydration, sustained attention was affected. Those who abstained from water for over 24 hrs (which equates to being dehydrated to the same level as exercising or being exposed to heat for up to 2hrs), reported difficulties in completing cognitive tasks. They were 20% more tired and 18% less alert and reported needing additional mental effort to complete the memory and attention tasks[4 Trusted Source 2005 - American Journal of physiology. Regulatory, Integrative and Comparative Physiology Human study Effect of water deprivation on cognitive-motor performance in healthy men and women ] . If you have a test coming up, having a glass of water just before you begin can improve your performance. A study where participants consumed 120-330ml water just before tests reported improvement in sustained attention, and those who drank more, performed better[5 Trusted Source 2019 - Nutrients Systematic and meta-analysis Narrative Review of Hydration and Selected Health Outcomes in the General Population ] . In some school students, adequate hydration improved attention test scores by 50%[6 Trusted Source 2021 - The Egyptian Journal of Community Medicine Human study Effect of Hydration Status of School Children on Cognitive Performance and Impact of Health Education on Their Drinking Behavior ] . During dehydration, the levels of the stress hormone, cortisol spike because your body assumes this to be a stressful situation. High levels of cortisol reduce your processing speed and short-term memory[7 Trusted Source 2014 - British Journal of Nutrition 3rd-party resource Effects of hydration status on cognitive performance and mood ] .
2 Improved mood and energy
If you are feeling low, it might be worth upping your fluids. Keeping yourself hydrated can help improve mood and energy levels. How long does it take to rehydrate your brain? It takes under 2 hours to rejuvenate your brain. Those who drank 500ml water following an overnight fast, reported 55% improvement in energy levels and 5% improvement in mood, after 90 minutes[8 Trusted Source 2020 - International Journal of Environmental Research and Public Health Human study Different Amounts of Water Supplementation Improved Cognitive Performance and Mood among Young Adults after 12 h Water Restriction in Baoding, China: A Randomized Controlled Trial (RCT) ] . People who drank less water (<1L/day) reported improvement in sleep, mood, and energy levels when they increased their intake to 2.5L/day for a week[9 Trusted Source 2014 - PLoS ONE Human study Effects of Changes in Water Intake on Mood of High and Low Drinkers ] .
3 Better physical performance
Proper hydration is vital for enhancing cardiovascular function, increasing endurance, and reducing fatigue during exercise. It helps maintain blood volume, allowing the heart to pump efficiently and deliver oxygen to muscles[10 Trusted Source 2006 - Gatorade Sports Science Institute 3rd-party source Hydration Assessment of Athletes ] ,[11 Trusted Source 2003 - Current Sports Medicine Reports Research evaluation Fluid Balance and Endurance Exercise Performance ] . Staying hydrated also delays fatigue by enabling muscles to work optimally, while supporting effective temperature regulation through sweating. Overall, adequate fluid intake is essential for both performance and safety during physical activities.
4 Support of vital bodily functions
Water is crucial for various bodily functions, including digestion, nutrient absorption, circulation, and waste elimination[12 Trusted Source 2008 - Clinical Nutrition ESPEN Research evaluation Basics in clinical nutrition: Water and electrolytes in health and disease ] . It aids in breaking down food, ensuring that nutrients are effectively absorbed into the bloodstream. Additionally, proper hydration helps maintain healthy blood pressure and supports efficient circulation, which is vital for overall health. Furthermore, adequate water intake can reduce the risk of urinary tract infections by diluting urine and promoting regular elimination of waste.
5 Brain structure
Since the brain is almost 80% fluid, lack of adequate hydration impacts the volume of the structures. 16 hours of dehydration reduced the brain volume by 0.55%, and when rehydrated by 1.5L water intake, the volume increased by 0.72%[13 Trusted Source 2022 - Frontiers in Nutrition Human study Dehydration and rehydration affect brain regional density and homogeneity among young male adults, determined via magnetic resonance imaging: A pilot self-control trial ] . Reduced brain volume has a negative impact on cognition and is a reason for lower cognition in old age. Those who were dehydrated due to low fluid intake (<150ml/day) were found to have a lower volume of brain cells and the connections between these cells[14 Trusted Source 2012 - PLoS ONE Human study Investigating Structural Brain Changes of Dehydration Using Voxel-Based Morphometry ] . This can help explain why you experience lower focus and brain fog when you are less hydrated because your brain is running at sub-optimal capacity.
How do you fix brain fog from dehydration?
All side effects of dehydration on the brain can be tackled by ensuring you drink around 6-8 glasses of fluid per day, including water, low-fat milk, and lower-sugar beverages including tea and coffee[15 Trusted Source 2019 - National Health Service 3rd-party source The Eatwell Guide ] . If you’re looking to be very precise, the European Food Safety Authority (EFSA) recommends women drink 2 litres and men drink 2.5 litres of water per day to maintain normal physical and cognitive functions[16 Trusted Source 2010 - EFSA Journal, Research evaluation Scientific Opinion on Dietary Reference Values for water ] . You can start by drinking 1-2 glasses upon waking up. Keeping a water bottle nearby can be a gentle reminder to sip regularly during the day. It is essential to top off any water losses and maintain a balance, especially in cases where you lose water due to being in hot and humid conditions or after a workout. You can also pay attention to urine colour and drink more if the colour is darker as this indicates dehydration[17 Trusted Source 2020 - Frontiers in Nutrition Research evaluation The Effect of Hydration on Urine Color Objectively Evaluated in CIE L*a*b* Color Space ] . Aim for light straw-coloured urine. Additionally, eating a diet filled with water-rich foods like fruits and vegetables can also help you maintain adequate hydration.
Staying properly hydrated is crucial for optimal brain function, ultimately supporting overall brain health and mental well-being.
References
[1] Oros-Peusquens et al. (2019). A Single-Scan, Rapid Whole-Brain Protocol for Quantitative Water Content Mapping With Neurobiological Implications. Frontiers in Neurology. https://doi.org/10.3389/fneur.2019.01333
[2] Kostelnik, S. B. et al. (2021). The Validity of Urine Color as a Hydration Biomarker within the General Adult Population and Athletes: A Systematic Review. Journal of the American College of Nutrition, 40(2), 172–179. https://doi.org/10.1080/07315724.2020.1750073
[3] MacLeod, H. et al. (2018). Effects of heat stress and dehydration on cognitive function in elite female field hockey players. BMC Sports Science, Medicine and Rehabilitation, 10(1) https://doi.org/10.1186/s13102-018-0101-9
[4] Szinnai, G. et al. (2005). Effect of water deprivation on cognitive-motor performance in healthy men and women. American journal of physiology. Regulatory, integrative and comparative physiology, 289(1), R275–R280. https://doi.org/10.1152/ajpregu.00501.2004
[5] Liska, D. et al. (2019). Narrative Review of Hydration and Selected Health Outcomes in the General Population. Nutrients, 11(1), 70. https://doi.org/10.3390%2Fnu11010070
[6] Samy, H. (2021). Effect of Hydration Status of School Children on Cognitive Performance and Impact of Health Education on Their Drinking Behavior. The Egyptian Journal of Community Medicine, 39(2) https://doi.org/10.21608/ejcm.2021.167557
[7] Masento, N.A. et al. (2014). Effects of hydration status on cognitive performance and mood. British Journal of Nutrition, 111(10), 1841–1852. https://doi.org/10.1017/S0007114513004455
[8] Zhang, J. et al. (2020). Different Amounts of Water Supplementation Improved Cognitive Performance and Mood among Young Adults after 12 h Water Restriction in Baoding, China: A Randomized Controlled Trial (RCT). International journal of environmental research and public health, 17(21), 7792. https://doi.org/10.3390/ijerph17217792
[9] Pross, N. et al. (2014). Effects of changes in water intake on mood of high and low drinkers. PloS one, 9(4), e94754. https://doi.org/10.1371%2Fjournal.pone.0094754
[10] Cheuvront, S. N., & Sawka, M. N. (2006). Hydration Assessment of Athletes. Gatorade Sports Science Institute. https://www.gssiweb.org/sports-science-exchange/article/sse-97-hydration-assessment-of-athletes
[11] Cheuvront, S. N., Carter, R., & Sawka, M. N. (2003). Fluid Balance and Endurance Exercise Performance. Current Sports Medicine Reports, 2(4), 202-208. https://doi.org/10.1249/00149619-200308000-00006
[12] Sobotka, L., Allison, S., & Stanga, Z. (2008). Basics in clinical nutrition: Water and electrolytes in health and disease. Clinical Nutrition ESPEN, 3(6), 259-266. https://doi.org/10.1016/j.eclnm.2008.06.004
[13] Zhang, N. et al. (2022). Dehydration and rehydration affect brain regional density and homogeneity among young male adults, determined via magnetic resonance imaging: A pilot self-control trial. Frontiers in nutrition, 9, 906088. https://doi.org/10.3389/fnut.2022.906088
[14] Streitbürger, D.-P. et al (2012). Investigating Structural Brain Changes of Dehydration Using Voxel-Based Morphometry. PLoS ONE, 7(8), e44195. https://doi.org/10.1371/journal.pone.0044195
[15] The Eatwell Guide (2019). NHS. https://www.nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/the-eatwell-guide/
[16] EFSA (2010). Scientific Opinion on Dietary Reference Values for water. EFSA Journal, 8(3). https://doi.org/10.2903/j.efsa.2010.1459
[17] Belasco, R. (2020). The Effect of Hydration on Urine Color Objectively Evaluated in CIE L*a*b* Color Space. Frontiers in nutrition, 7, 576974. https://doi.org/10.3389%2Ffnut.2020.576974
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