Influence of progressive fluid restriction on mood and physiological markers of dehydration in women

Abstract

The present study evaluated, using a well-controlled dehydration protocol, the effects of 24 h fluid deprivation (FD) on selected mood and physiological parameters. In the present cross-over study, twenty healthy women (age 25 (se 0·78) years) participated in two randomised sessions: FD-induced dehydration v. a fully hydrated control condition. In the FD period, the last water intake was between 18.00 and 19.00 hours and no beverages were allowed until 18.00 hours on the next day (23–24 h). Water intake was only permitted at fixed periods during the control condition. Physiological parameters in the urine, blood and saliva (osmolality) as well as mood and sensations (headache and thirst) were compared across the experimental conditions. Safety was monitored throughout the study. The FD protocol was effective as indicated by a significant reduction in urine output. No clinical abnormalities of biological parameters or vital signs were observed, although heart rate was increased by FD. Increased urine specific gravity, darker urine colour and increased thirst were early markers of dehydration. Interestingly, dehydration also induced a significant increase in saliva osmolality at the end of the 24 h FD period but plasma osmolality remained unchanged. The significant effects of FD on mood included decreased alertness and increased sleepiness, fatigue and confusion. The most consistent effects of mild dehydration on mood are on sleep/wake parameters. Urine specific gravity appears to be the best physiological measure of hydration status in subjects with a normal level of activity; saliva osmolality is another reliable and non-invasive method for assessing hydration status.

National Athletic Trainers' Association Position Statement: Fluid Replacement for the Physically Active

“…At greater water deficits (more than 2% body mass loss), dizziness, headache, vomiting, nausea, heat sensations on the head or neck, chills, and dyspnea may be present (Table 1). 50,57,139 The degree of hypohydration, mental status, and general medical condition of the athlete will dictate the mode, amount, type, and rate of recommended rehydration.…”

“…181,195,199,200 At similar hypohydration levels, women seemed to demonstrate fewer consistent cognitive impairments but more mood-state decrements than men. 8,9,139 Furthermore, heat exposure may induce a more profound negative effect of hypohydration on mood state in both men and women. 195,198,199 Fluid Replacement…”

Hydration in Children: What Do We Know and Why Does it Matter?

“…However, the association between early childhood and later life intake has never been demonstrated for drinking water, due to the scarcity of longitudinal studies assessing water intake. But if indeed drinking habits (i.e., plain water intake in particular) were sustained throughout life, children who drink little water would become adults who drink little water with potential consequences for kidney [10] and metabolic health [11,12] as well as cognitive and mood impairments [13,14]. During early childhood, the acquisition of eating and drinking behavior is mainly driven by adults since children depend upon them for the provision of food and beverages, and adults serve as role models which children copy and acquire habits from.…”

Effects of Dehydration on Brain Functioning: A Life-Span Perspective

“…This dissociation between the effect of mild dehydration on performance and mood in young healthy women has been confirmed by another group of researchers. In a study evaluating the effect of an acute fluid restriction on mood and cognition, 20 young healthy women (mean age: 25 ± 3.5 years) underwent a randomized 2-period crossover study [14] . During the fluid restriction period, participants were asked to refrain from drinking for 24 h. During the control condition, water intake (a total of 2 L) was allowed at fixed time points and was dissociated from meals so that eating was similar for both periods.…”