Not drinking enough water triggers stronger stress response: Study

A recent study has found that people who fail to drink enough water each day may experience a stronger biological reaction to stress, the Irish broadcaster RTE reported on Friday.

Researchers at Liverpool John Moores University discovered that individuals with low daily fluid intake released higher levels of cortisol, the body’s main stress hormone, when subjected to stressful situations, even though they did not feel thirstier than those who consumed more.

The study, published in the Journal of Applied Physiology, compared two groups of 16 adults each.

One group habitually drank less than 1.5 liters (around 0.4 gallons) of water per day, while the other met European Food Safety Authority guidelines of around 2.5 liters (0.6 gallons) for men and 2 liters (0.5 gallons) for women.

Participants’ hydration levels were tracked over a week before they took part in a stress test involving a surprise job interview and a mental arithmetic challenge in front of a panel.

Saliva samples collected before and after showed that cortisol levels spiked significantly higher among those with lower fluid intake.

“People who have a low daily fluid intake, who don’t meet the recommendations, are likely to be poorly hydrated,” said Neil Walsh from the university's School of Sport and Exercise Sciences.

“But what we didn’t know was whether, when you then stress those people under controlled conditions, they would have a greater stress hormone response.”

The researchers found that both groups reported similar levels of anxiety and had comparable increases in heart rate during the test. However, only the under-hydrated group displayed greater cortisol reactivity.

Walsh warned that exaggerated cortisol responses are linked to long-term health risks, including heart disease, diabetes, and depression.

“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,” he added.