Overview

• Adults habitually drinking under roughly 1.5 liters per day showed more than a 50% greater cortisol response in laboratory stress testing.
• The peer-reviewed Journal of Applied Physiology study monitored 32 healthy adults for seven days, then used the Trier Social Stress Test.
• Low-intake participants felt just as anxious and had similar heart-rate rises, yet produced higher cortisol and had darker, more concentrated urine.
• Authors emphasize the small, short, observational design cannot prove causation and they call for randomized, longer-term trials.
• Coverage points to existing NHS guidance of about six to eight glasses of fluid daily as a practical, low-risk target while evidence builds.