Overview

• The peer-reviewed study from Liverpool John Moores University was published August 22, 2025 in the Journal of Applied Physiology.
• Adults who habitually drank under 1.5 liters per day showed a cortisol response to an acute stress task more than 50% higher than those meeting EFSA intake guidelines.
• The trial enrolled 32 healthy young adults, tracked hydration for one week via urine and blood markers, then used the Trier Social Stress Test with saliva cortisol sampling.
• Despite similar self-reported anxiety and heart-rate increases across groups, only the low-intake group exhibited a significant cortisol spike.
• Authors emphasize the small sample and lab setting, reference existing guidance of about 2.0 liters for women and 2.5 liters for men, and suggest practical habits like keeping a water bottle as further studies assess real-world impact.