Overview
- In a Liverpool John Moores University study in the Journal of Applied Physiology, adults drinking under 1.5 liters per day showed roughly 50% higher cortisol reactivity to an acute stressor than peers meeting fluid guidelines.
- The protocol monitored intake for one week and then applied the Trier Social Stress Test, with 32 participants selected from 62 screened based on habitual fluid consumption.
- Both groups reported similar anxiety and heart-rate increases, yet only the low-intake group exhibited a significant rise in saliva cortisol during the test.
- Objective assessments indicated poorer hydration in the low-intake group, including darker and more concentrated urine.
- Researchers recommend following intake targets of about 2.0 liters for women and 2.5 liters for men and using urine color as a simple check, while emphasizing that the small, short-term design warrants randomized and long-term studies.