Key Takeaways
Dehydration spikes stress hormones. People who drank less than 1.5 liters of water daily showed a 50% increase in cortisol, the body’s main stress hormone.Hydration directly affects your brain. Low fluid intake activates vasopressin, which impacts the brain’s stress response and raises cortisol levels—even if you don’t feel thirsty.Simple fixes help. Keeping water nearby and checking urine color (light yellow = hydrated) are easy ways to stay on top of your hydration goals and manage stress.
Whether you’re someone who carries a water bottle everywhere they go or always needs to borrow from a friend, sufficient hydration is an essential part of a healthy lifestyle. But with so many dehydrating products on the market—like alcoholic beverages, salty foods, and sugary syrups—it’s not always an easy goal to achieve. You might notice how the less water you drink, the worse you feel, especially when it comes to managing stress. And you’re not the only one who feels that way: according to a recent study conducted by Liverpool John Moores University and published in the Journal of Applied Physiology, individuals who drank less than one and a half liters of water per day had a 50% increase in cortisol levels compared to those who met the ideal daily water intake.
“Cortisol is the body’s primary stress hormone, and exaggerated cortisol reactivity to stress is associated with an increased risk of heart disease, diabetes, and depression,” says Professor Neil Walsh, study lead. “If you know you have a looming deadline or a speech to make, keeping a water bottle close could be a good habit with potential benefits for your long-term health.”
The Link Between Dehydration and Stress
To find the link between dehydration and cortisol levels, researchers divided healthy young adults into two equal-sized groups, with one group maintaining a high fluid intake and the other a low fluid intake. “Participants maintained their usual drinking habits for one week, during which hydration levels were monitored in blood and urine samples,” the study explains. “Then participants underwent the Trier Social Stress Test, widely used to simulate real-world stress through a mock job interview and a mental arithmetic task.” While both groups showed some anxiety towards the test, the low fluid intake group showed a significant increase in saliva cortisol. Poor hydration correlated with significant cortisol reactivity, even though participants said they did not feel thirsty.
Neurologically, when the body senses dehydration, it triggers the release of vasopressin—a hormone which, beyond acting on the kidneys, also impacts the brain’s stress response center called the hypothalamus. As it reaches the hypothalamus, water influences the release of cortisol and naturally helps your body manage stress. “If you know, for example, that you have a stressful schedule, maybe a looming deadline or a speech to make, keeping a water bottle close could be a good habit with potential benefits for your long-term health,” suggests Dr. Daniel Kashi, a member of the study team.
One simple and effective way to know if you’re drinking enough water is to check the toilet after urinating. A light yellow color typically indicates that you’re hydrated, whereas a darker yellow might mean that you’re dehydrated. To increase your daily water intake—and lower your stress hormones—aim to keep a water bottle by your bedside, at your desk, or carry one with you when you leave the house.