NAIROBI, Kenya – Failing to stay properly hydrated may do more than leave you parched—it could also amplify your body’s stress response and increase vulnerability to chronic diseases, new research suggests.
A study by Liverpool John Moores University (LJMU) has found that people who drank less than 1.5 litres of fluid daily—roughly the equivalent of seven cups of tea—recorded stress hormone spikes more than 50 per cent higher than those who met hydration guidelines.
The research, published in the Journal of Applied Physiology, highlights how under-hydration can magnify cortisol levels.
Cortisol, often referred to as the body’s “primary stress hormone,” plays a crucial role in regulating mood, metabolism, and immune function.
But repeated surges are linked to long-term health problems, including heart disease, diabetes, and depression.
“Cortisol is vital in helping the body cope with stress, but exaggerated responses are linked to poor long-term health,” said study lead Professor Neil Walsh of LJMU’s School of Sport and Exercise Sciences. “If you know you’ve got a looming deadline or a big presentation, keeping a water bottle nearby could be a simple but meaningful habit.”
Testing Stress Under Pressure
The research tracked two groups of healthy young adults: those in the lowest 25 per cent of daily fluid intake and those in the highest.
For one week, participants maintained their usual drinking patterns, with hydration levels measured through blood and urine samples.
They were then put through the Trier Social Stress Test—a lab challenge combining a mock job interview and mental arithmetic—designed to mimic real-world stress.
While both groups reported similar levels of anxiety and showed comparable increases in heart rate, only the low-fluid group experienced a significant surge in cortisol.
Surprisingly, they did not necessarily feel thirstier, but urine tests showed darker, more concentrated samples—a clear marker of under-hydration.
Why It Happens
Co-author Dr Daniel Kashi explained that dehydration prompts the body to release vasopressin, a hormone that helps conserve water. But vasopressin also activates the brain’s stress centre, pushing cortisol higher.
“Over time, that exaggerated stress response may take a toll on long-term health,” Dr Kashi said. “Being hydrated may help your body handle stress more effectively. A simple way to check is to monitor your urine colour—pale yellow is a good sign. But do not overhydrate.”
Daily Recommendations
Current guidelines suggest women aim for about 2 litres of fluid a day and men 2.5 litres, with water, tea, coffee, and even water-rich foods such as cucumbers and watermelon all counting towards the total.
As daily stress levels rise for many, the study underscores that one of the simplest tools for resilience might already be within easy reach: a glass of water.