Healthcare (Commonwealth Union) – When our body has insufficient water, it may elevate our susceptibility to stress-linked health problems, according to a recent study from Liverpool John Moores University (LJMU).
Scientists discovered that individuals who drink less than the advised daily number of fluids demonstrate a stronger stress hormone reaction, which is tied to an increased likelihood of resulting in heart disease, diabetes, and depression.
The study, released recently in the Journal of Applied Physiology and highlighted in The Conversation, revealed that individuals drinking under 1.5 litres of fluid—or the equivalent of about seven cups of tea—each day had stress-related cortisol levels more than 50% higher than those who met recommended hydration guidelines.
Professor Neil Walsh, who heads the study and teaches physiology at LJMU’s School of Sport and Exercise Sciences, indicated that cortisol is the main hormone the body releases during stress, and an overactive cortisol response has been linked to a higher likelihood of developing heart disease, diabetes, and depression.
He further pointed out that if we are facing an important deadline or preparing to give a talk, having water on hand and staying hydrated might be a simple habit that supports our long-term health.
Funded by Danone R&I, Neil and his team split healthy young adults into two groups based on their daily fluid consumption, representing the lowest and highest 25% of intake. The ‘low fluid’ group included people who usually drank less than 1.5 litres of fluids per day, including water and hot beverages. The ‘high fluid’ group consisted of individuals who consistently met daily hydration guidelines — 2 litres for women and 2.5 litres for men. Both the groups had a matching for factors known to play a role in stress responses, like psychological traits and sleep patterns.
The participants proceeded further with their normal drinking routines for one week while researchers noted the hydration with blood and urine tests. After this period, they completed the Trier Social Stress Test, a standard method for mimicking real-life stress using a mock job interview and a mental arithmetic challenge.
Dr. Daniel Kashi, who played a role in the research, pointed out that both groups saw similar levels of anxiety and showed comparable elevations in heart rate when the stress test was happeing. However, only the ‘low fluid’ group exhibited a significant rise in saliva cortisol in response to stress.
Excessive cortisol reactivity to stress has been linked to long-term health risks.
The explanation lies in the body’s system for regulating water, which is closely linked to the brain’s stress-control centre. Researchers pointed out that when the body identifies dehydration—irrespective of it being from not drinking sufficient fluids or from losing too much—it brings about the release of a hormone known as vasopressin. This hormone primarily targets the kidneys, encouraging them to reabsorb water to preserve blood volume and maintain the balance of electrolytes. However, this conservation process comes with a trade-off. Prolonged vasopressin release puts extra pressure on the kidneys, which must work harder to concentrate urine and regulate electrolytes.
Vasopressin also affects the brain’s stress hub, the hypothalamus, where it can influence cortisol production. In this way, vasopressin helps protect blood volume and electrolyte levels but simultaneously elevates the cortisol levels.
The researchers note that, although more long-term research is needed, these findings support existing guidance on daily fluid intake—around 2 litres for women and 2.5 litres for men.
“Being hydrated may help your body manage stress more effectively,” said Dr Kashi pointing out that it is a practical method to check our hydration status is to monitor our urine colour, where light yellow generally means good hydration.
“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.”
