Abstract
There is conflicting evidence as to whether water drinking elicits a pressor response in healthy young adults. The inclusion of a variable number of women may have contributed to the discrepancies found in past research. Thus, we aimed at exploring whether the osmopressor response follows a sexually dimorphic pattern. In a randomized fashion, 31 healthy adults (16 men; 15 women, aged 18-40years) ingested 50 and 500ml of water before completing a resting protocol on two separate days. Arterial blood pressure, heart rate and spectral heart rate variability were measured in the seated position at pre- and post-25min of water ingestion. Women responded to 500ml of water with a greater proportion of change in diastolic and mean arterial pressure (MAP) (P<0.05). Conversely, the percent change in systolic blood pressure (SBP) and heart rate was not different between sexes after 500ml of water. Overall, women demonstrated lower blood pressure, but higher resting heart rate compared with men (P<0.05). In contrast, heart rate variability was similar between sexes before and after ingesting either volume of water. There was a bradycardic effect of water and, irrespectively of sex; this was accompanied by increased high frequency power (HF) (P<0.05). We conclude that women display a greater magnitude of pressor response than men post-water ingestion. Accordingly, we provide direct evidence of sexual dimorphism in the haemodynamic response to water intake in young healthy adults.
Highlights
There is general agreement that water ingestion causes many physiological changes in the human body, including fluctuations in endocrine function, cardiovascular autonomic regulation and fluid balance [1,2,3,4]
We obtained a sex main effect for systolic blood pressure (BP) (F = 13.4, P < 0.05), diastolic BP (F = 9.5, P < 0.05), mean arterial pressure (MAP) (F = 7.7, P < 0.05) and heart rate (F = 4.2, P < 0.05); indicating that overall arterial pressure values were lower, whereas resting heart rate was higher in women than men
It was demonstrated that the overall haemodynamic response to water ingestion is more pronounced in women than in men
Summary
There is general agreement that water ingestion causes many physiological changes in the human body, including fluctuations in endocrine function, cardiovascular autonomic regulation and fluid balance [1,2,3,4]. It has been previously reported that the haemodynamic effects of drinking 500 ml of water are largely attenuated in liver transplant recipients, but remain well preserved in in patients with high-level spinal cord injuries [7,8]. This indicates that the vascular response to water ingestion is triggered by hypoosmolarity within the hepatic portal system and may involve a spinal reflex-like mechanism [7,8,9,10]. A more discrete, but significant, pressor effect was described
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