Before an important presentation, we check the slides, the microphone and the internet connection. Then we stand up to speak and discover that our mouth has gone dry. We have tested everything except the speaker.
Nervousness can cause dryness even when we have drunk adequately. But behind that familiar discomfort lies a less familiar question: does our water intake affect how the body responds to stress?
In 2025, researchers at Liverpool John Moores University investigated 32 healthy adults with habitually low or high fluid intake. After a week of monitoring, participants faced a mock job interview and mental arithmetic before an audience, an experience few would volunteer to repeat.
Both groups reported similar increases in anxiety, with similar heart-rate rises. Yet those drinking less, whose urine was more concentrated, showed greater cortisol reactivity. Comparable nervousness, different hormonal responses: what people reported did not reveal everything their bodies were doing.
The groups averaged approximately 1.3 and 4.4 litres of fluid daily. Those figures describe existing habits, not recommended targets. This small, Danone-funded comparison cannot prove that prescribing more water would reduce anxiety or prevent illness.
Still, the finding is biologically reasonable. Vasopressin helps the kidneys conserve water and helps regulate cortisol release. Water balance and the stress response share some physiological machinery. Researchers must now establish more clearly what changing drinking habits actually changes.
What interests me as a physician is how easily the physical circumstances of a difficult day disappear from its telling. We remember the argument, the deadline, the remark. Whether we ate, slept or drank adequately seems too ordinary to mention.
Yet ordinary needs can be postponed during a busy day. You notice thirst during a call. Afterwards, you tell yourself. Afterwards becomes a journey. You delay drinking again because you do not know where you will find a clean toilet.
By evening, you can recall every interruption but scarcely remember taking a break. Nothing seemed urgent enough to stop for. Looking back, it is difficult to identify when there was supposed to have been time.
This research does not explain that entire day. Cortisol is neither a complete measure of distress nor a substance we should spend our lives trying to suppress. It gives us a reason to investigate hydration, without reducing human difficulty to a bottle.
The useful response is undramatic. Keep water accessible. Drink regularly, including with meals. Usually, pale-yellow urine offers a practical clue; heat, sweating and activity increase requirements. Plan breaks during long stretches of work or travel.
Tea and coffee also count as fluids, although caffeine can make sensitive people jittery. If repeated cups leave you feeling more nervous, reconsider how much you are having rather than assuming every cup helps you cope.
Avoid forcing large quantities to meet an arbitrary target. Follow prescribed fluid restrictions, and seek assessment for persistent excessive thirst, frequent urination or recurring symptoms. These deserve more attention than simply increasing your water intake.
Persistent anxiety deserves appropriate care. Adequate drinking can accompany that care without replacing it. Meeting a physical need is worthwhile even when it does not resolve the distress that brought someone to the clinic.
Have some water before the difficult conversation. You cannot always make the problem smaller. You can stop asking your body to face it thirsty.
