Thirsty for answers: new study tests if water really quenches thirst

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

All randomized participants must have complete data from 4 weeks of screening. All inclusion criteria below must be met: * 4 weeks of 3-day mean total water intake of 35 ml/kg body weight * 4 weeks of \<1L/d drinking water * 4 weeks of \<1 hr/d moderate or vigorous physical activity given daily life conditions in Salzburg, Austria * No history of chronic disease * Normal blood pressure, * Normal blood chemistry and complete blood count (CBC) test results * Normal overnight urine concentration, and normal acute urine dilution after 500mL drinking water * Normal weight and height between 160-170 cm for women and 175-185 cm for men) * After overnight food and water restriction urine osmolality above 800 mmol/kg, salivary osmolality above 100 mmol/kg, and a thirst score below 70 mm on a 100 mm visual analog scale. Exclusion Criteria: * Individuals will be excluded from participation if the gender-specific target numbers have already been reached * Perceived stress score of \> 20 at any time during Weeks 1-4 * Schedule that does not allow continuous study participation * Intention to spend more than a day outside the Salzburg area during the study period (to reduce exposure to ground water with different background D2O as potential source of error) * Headache within the last six months * Pregnant, planning a pregnancy, or irregular or unknown menstrual cycle * Active use of tobacco or e-cigarettes * Daily consumption of alcohol * Regular use of medication * Agoraphobia or claustrophobia that would prevent brain fMRI testing * Metal-containing intrauterine device (IUD) that would prevent fMRI testing * Doubtful or unwilling to complete all study procedures (including drinking alcohol; drinking plain tap water, blood tests, 24-hour urine collection, fMRI scans, and stable isotope tests) * Unwilling to be randomly assigned to intervention or control * Incomplete baseline data in Weeks 1-4 (including blood tests, 24-hour urine collection, and MRI scans).