We all know that hydration is important. But did you know that hydration is directly correlated to your brain and cognitive function? So next time you go to grab that afternoon cup of coffee, you might want to consider grabbing a glass of water instead.

After going through over 13 scientific studies linking hydration to focus, here’s what we found.

In a 101-person study, individuals were exposed to a climate controlled room at 86°F for four hours. They randomly assigned one group to drink no water and one group to drink 300ml water during that time. At three times during the four-hour period, the scientists measured urine hydration status, body mass, attention, memory, and mood. The results showed for the first time that even slight dehydration can reduce brain function and drinking enough water to demonstrate adequate hydration on urine studies was associated with improved cognitive functioning.

Another controlled clinical trial separated 52 school aged children into two experimental groups: one group got 750ml water over a two-hour period after breakfast and the other didn’t. They measured hydration status with urine testing. Then, they did extensive cognitive testing to assess brain function. They found that the children whose urine testing showed improved hydration status did better on cognitive testing, and suggested that regular assessment of hydration status over time may be a key for cognitive enhancement.

A more recent randomized, controlled trial in October 2020 took it one step further. 64 young adults fasted for 12 hours overnight, and hydration status and cognitive performance were tested in the morning. They were then divided randomly into four groups: no water, 100ml water, 200ml water, and 500ml water, and were told to consume the water within 10 minutes. After 90 minutes, blood and urine hydration testing was done as well as repeat cognitive testing of brain function. They found that water supplementation improved working memory, reduced anger and fatigue, and that the group with the highest hydration status had the best cognitive performance.

Ready to track your hydration levels so you can stay more alert and focused amidst the chaos of working from home? Vessel not only reminds you to drink water, but tells you exactly how many ounces your body needs by testing your hydration in your urine.


Benton D, Jenkins KT, Watkins HT, Young HA. Minor degree of hypohydration adversely influences cognition: a mediator analysis. Am J Clin Nutr. 2016 Sep;104(3):603-12. doi: 10.3945/ajcn.116.132605. Epub 2016 Aug 10. PMID: 27510536.

Perry CS 3rd, Rapinett G, Glaser NS, Ghetti S. Hydration status moderates the effects of drinking water on children’s cognitive performance. Appetite. 2015 Dec;95:520-7. doi: 10.1016/j.appet.2015.08.006. Epub 2015 Aug 10. PMID: 26271221.

Zhang J, Zhang N, He H, Du S, Ma G. 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). Int J Environ Res Public Health. 2020 Oct 24;17(21):7792. doi: 10.3390/ijerph17217792. PMID: 33114364; PMCID: PMC7662706. 


Key takeaway

  • Increasing water intake can improve cognitive functioning.

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Reviewed by Dr. Dave Larson