Individuals consuming under 1.5 litres of water daily experience elevated cortisol levels when faced with stressful situations, a study has revealed.
The research discovered that people with insufficient water intake demonstrate heightened biological stress responses, even though they report no increased sensation of thirst compared to those meeting hydration guidelines.
Scientists from Liverpool John Moores University propose that maintaining accessible water supplies during demanding periods may offer significant health advantages, particularly given the established connections between excessive cortisol production and serious conditions including cardiovascular disease, diabetes and depression.
Leaving elevated cortisol unmanaged can also set the stage for weight gain, high blood pressure and mood swings.
Hydration may play an underappreciated role in stress management
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The findings suggest hydration plays a previously under-appreciated role in stress management.
The investigation involved 32 participants divided equally between those consuming below 1.5 litres daily and those adhering to recommended fluid intake levels.
European Food Safety Authority standards were applied, which specify 2.5 litres for men and two litres for women, while UK guidelines recommend six to eight cups daily, approximately 1.5 to two litres.
Scientists tracked participants' hydration status across a week through blood and urine analysis before conducting laboratory stress assessments.
The research team acknowledged that fluid requirements may increase in hot conditions, during physical activity, illness recovery, pregnancy or breastfeeding periods.
The stress assessment required participants to undertake an unexpected job interview with only ten minutes' preparation time.
Subjects then faced a panel of three white-coated assessors while being recorded by a mock camera, followed by a rapid mental arithmetic exercise involving sequential number subtraction.
Professor Neil Walsh from LJMU's School of Sport and Exercise Sciences characterised the experience as "really flustering".
Saliva samples collected before and after the assessment revealed significantly elevated cortisol concentrations in the low-hydration group, despite both cohorts reporting comparable anxiety levels and physiological responses, including accelerated heart rates, perspiration and oral dryness.
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Regular hydration could offer potential benefits for long-term health
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Professor Walsh noted that while both groups experienced identical anxiety and physical stress indicators, those with inadequate hydration showed "much greater cortisol responses".
He explained: "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."
The professor recommended: "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."
Further investigation aims to determine whether improving water consumption might help mitigate reactions to everyday stressors such as congested traffic or workplace presentations.