Study links low fluid intake to higher cortisol response under stress

A new study by researchers at Liverpool John Moores University found that adults who habitually drink less than about 1.5 liters of fluid a day show markedly larger spikes in cortisol, the body's primary stress hormone, when exposed to acute psychosocial stress. The research, published recently in the Journal of Applied Physiology, monitored young adults over a week and then subjected them to a standardized laboratory stress challenge in Liverpool, finding that lower fluid intake was associated with substantially greater hormonal stress responses.

Researchers divided participants into two groups based on their usual fluid consumption. In the study sample, which consisted of 32 healthy young adults, the low-intake group averaged roughly 1.3 liters a day while the higher-intake group averaged about 4.4 liters in the reported data. Hydration was tracked with urine tests and other measures, and participants completed the Trier Social Stress Test, a protocol that includes a surprise mock job interview and timed mental arithmetic. Saliva samples taken before and after the tasks showed that those with lower habitual fluid intake experienced cortisol increases of roughly 50 percent or...