In the fast-paced life of the average person, where long work hours, traffic congestion, and hot, humid climates are the norm, hydration is often overlooked. According to The Indian Express, nearly 75 per cent of Indians do not consume adequate water daily, leaving many in a state of chronic mild dehydration. While water is essential for basic bodily functions, its role in regulating stress hormones, such as cortisol, is increasingly evident. Cortisol, produced by the adrenal glands, helps the body respond to stress, but chronically elevated levels can lead to sleep disturbances, weight gain, and weakened immunity. Emerging research shows that even mild dehydration can amplify cortisol production, making proper hydration a simple yet powerful tool for managing stress and supporting overall health.

The Science: Hydration Status and Cortisol Reactivity

Recent studies have begun to map how hydration status (i.e., how well hydrated one is) influences cortisol reactivity (i.e., how strongly cortisol rises in response to stress).

“Habitual fluid intake and hydration status influence cortisol reactivity to acute psychosocial stress” (2025, Journal of Applied Physiology)

In a controlled experiment, researchers divided healthy adults into ‘low fluid intake’ and ‘high fluid intake’ groups. They assessed hydration via urinary osmolality and other biomarkers. They then exposed both groups to a standard psychosocial stress test (public speaking plus mental arithmetic). The low-fluid group (i.e., suboptimal hydration) exhibited greater cortisol reactivity. They also found a strong correlation between hydration (urine concentration) and cortisol rise.

“Relationship between fluid intake, hydration status and cortisol dynamics” (2024, ScienceDirect)

This observational study found that markers of suboptimal hydration (e.g., higher urinary osmolality, lower urine volume) were associated with altered cortisol dynamics (such as higher basal cortisol or altered diurnal slopes) in habitual settings.

“Basal Mild Dehydration Increases Salivary Cortisol After a Friendly Match” (2018, Frontiers)

In this sports-physiology study, young soccer players in a mildly dehydrated state showed a 28 per cent increase in salivary cortisol after a match, whereas well-hydrated peers showed no significant rise. This suggests that even moderate dehydration acts as an additional stressor on top of exercise.

Collectively, these studies suggest that suboptimal hydration amplifies the body’s cortisol response to stressors, whether psychological or physical.

Related Story: Hydration 101: Before, During and After Exercise

Biological Mechanisms: How Might Dehydration Influence Cortisol?

• Vasopressin (antidiuretic hormone): When dehydration is sensed, the body releases vasopressin to conserve water. But vasopressin also interacts with the hypothalamic-pituitary-adrenal (HPA) axis, sensitising it and promoting cortisol release under stress.
• Osmotic stress: Changes in plasma osmolality influence central osmoreceptors, which can modulate stress circuits in the brain.
• Homeostatic load: Mild dehydration itself is a physiological stressor; the body may treat it as an additional burden, amplifying the HPA axis response.

In short, inadequate hydration forces the body to juggle water balance and stress, potentially worsening cortisol surges.

Related Story: Chronic Dehydration: How UR.Life OHC Nurse Can Help

Hydration Strategies to Modulate Cortisol

• Set a daily fluid goal: For many adults, aim for at least 1.8 to 2.5 litres of water (or fluids) per day, adjusting upward on hot or humid days, or during activity.
• Distribute intake evenly: Sip water regularly across the day, rather than drinking large volumes only when thirsty (thirst is often a late signal).
• Check urine colour: Pale yellow urine generally indicates decent hydration; darker urine suggests more concentrated fluids.
• Include hydrating foods: Fruits like watermelon, cucumber, oranges, and soups can contribute. In Indian kitchens, rasam, buttermilk (chaas), and coconut water are useful.
• Carry a water bottle: At work, school, commuting, make it a habit to sip rather than wait.
• Avoid overhydration or electrolyte imbalance: Don’t force excessive water intake in one go. In hot climates, pairing small amounts of water with electrolytes (e.g., a pinch of salt) can help maintain balance.
• Time your intake with stress: If you know you have a stressful meeting, exam, or performance ahead, ensure you are well hydrated beforehand for a calmer cortisol response.

Related Story: 10 Tips For Better Hydration

Maintaining optimal hydration is a straightforward, low-cost strategy that may dampen cortisol surges and support stress resilience. For many, it could be one of the simpler tools in your stress management toolkit, especially in hot summers or hectic workdays. It’s about small, mindful choices that nurture balance from within. Start from here, get all your wellness solutions in one place. A whole new world awaits just a click away.