Cardiovascular responses to water drinking: does osmolality play a role?
ABSTRACT Water drinking activates the autonomic nervous system and induces acute hemodynamic changes. The actual stimulus for these effects is undetermined but might be related to either gastric distension or to osmotic factors. In the present study, we tested whether the cardiovascular responses to water drinking are related to water's relative hypoosmolality. Therefore, we compared the cardiovascular effects of a water drink (7.5 ml/kg body wt) with an identical volume of a physiological (0.9%) saline solution in nine healthy subjects (6 male, 3 female, aged 26 +/- 2 years), while continuously monitoring beat-to-beat blood pressure (finger plethysmography), cardiac intervals (electrocardiography), and cardiac output (thoracic impedance). Total peripheral resistance was calculated as mean blood pressure/cardiac output. Cardiac interval variability (high-frequency power) was assessed by spectral analysis as an index of cardiac vagal tone. Baroreceptor sensitivity was evaluated using the sequence technique. Drinking water, but not saline, decreased heart rate (P = 0.01) and increased total peripheral resistance (P < 0.01), high-frequency cardiac interval variability (P = 0.03), and baroreceptor sensitivity (P = 0.01). Neither water nor saline substantially increased blood pressure. These responses suggest that water drinking simultaneously increases sympathetic vasoconstrictor activity and cardiac vagal tone. That these effects were absent after drinking physiological saline indicate that the cardiovascular responses to water drinking are influenced by its hypoosmotic properties.
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ABSTRACT: Energy drinks are beverages containing vasoactive metabolites, usually a combination of caffeine, taurine, glucuronolactone and sugars. There are concerns about the safety of energy drinks with some countries banning their sales. We determined the acute effects of a popular energy drink, Red Bull, on cardiovascular and hemodynamic variables, cerebrovascular parameters and microvascular endothelial function. Twenty-five young non-obese and healthy subjects attended two experimental sessions on separate days according to a randomized crossover study design. During each session, primary measurements included beat-to-beat blood pressure measurements, impedance cardiography and transcranial Doppler measurements for at least 20 min baseline and for 2 h following the ingestion of either 355 mL of the energy drink or 355 mL of tap water; the endothelial function test was performed before and two hours after either drink. Unlike the water control load, Red Bull consumption led to increases in both systolic and diastolic blood pressure (p < 0.005), associated with increased heart rate and cardiac output (p < 0.05), with no significant changes in total peripheral resistance and without diminished endothelial response to acetylcholine; consequently, double product (reflecting myocardial load) was increased (p < 0.005). Red Bull consumption also led to increases in cerebrovascular resistance and breathing frequency (p < 0.005), as well as to decreases in cerebral blood flow velocity (p < 0.005) and end-tidal carbon dioxide (p < 0.005). Our results show an overall negative hemodynamic profile in response to ingestion of the energy drink Red Bull, in particular an elevated blood pressure and double product and a lower cerebral blood flow velocity.European Journal of Nutrition 01/2014; · 3.13 Impact Factor
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ABSTRACT: AimDrinking water induces short-term cardiovascular and metabolic changes. These effects are considered to be triggered by gastric distension and osmotic factors but little is known about the influence of water temperature.Methods We determined, in a randomized crossover study, the acute cardiovascular and metabolic responses to 500mL of tap water at 3°C (cold), at 22°C (room), and at 37°C (body) in 12 young humans to ascertain an effect of water temperature. We measured continuous beat-to-beat hemodynamics, skin blood flux with laser Doppler flowmetry, and resting energy expenditure by indirect calorimetry starting with a 30 min baseline followed by a 4 min drink-period and a subsequent 90 min post-drink observationResultsIngestion of cold- and room-tempered water led to decreased heart rate (P<0.01) and double product (P<0.01), and increased stroke volume (P<0.05); these effects were not observed with body-tempered water. Drinking cold- and room-, but not body-tempered water, led to increased high frequency power of heart rate variability (P<0.05) and baroreflex sensitivity (P<0.05). Cold- and room-tempered water increased energy expenditure over 90 min by 2.9% (P<0.05) and 2.3% (ns), respectively, accompanied by a diminished skin blood flux (P<0.01), thereby suggesting that both small increases in heat production together with decreased heat loss contribute to warming up the ingested water to intra-abdominal temperature levels.Conclusions Overall, ingestion of cold- and room-, but not body-tempered water reduced the workload to the heart through a reduction in heart rate and double product which could be mediated by an augmented cardiac vagal tone.This article is protected by copyright. All rights reserved.Acta Physiologica 03/2014; · 4.38 Impact Factor
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ABSTRACT: Overconsumption of sugar-sweetened beverages has been implicated in the pathogenesis of CVD. The objective of the present study was to elucidate acute haemodynamic and microcirculatory responses to the ingestion of sugary drinks made from sucrose, glucose or fructose at concentrations similar to those often found in commercial soft drinks. In a randomised cross-over study design, twelve young healthy human subjects (seven men) ingested 500 ml tap water in which was dissolved 60 g of either sucrose, glucose or fructose, or an amount of fructose equivalent to that present in sucrose (i.e. 30 g fructose). Continuous cardiovascular monitoring was performed for 30 min before and at 60 min after ingestion of sugary drinks, and measurements included beat-to-beat blood pressure (BP) and impedance cardiography. Additionally, microvascular endothelial function testing was performed after iontophoresis of acetylcholine and sodium nitroprusside using laser Doppler flowmetry. Ingestion of fructose (60 or 30 g) increased diastolic and mean BP to a greater extent than the ingestion of 60 g of either glucose or sucrose (P< 0·05). Ingestion of sucrose and glucose increased cardiac output (CO; P< 0·05), index of contractility (P< 0·05) and stroke volume (P< 0·05), but reduced total peripheral resistance (TPR; P< 0·05), which contrasts with the tendency of fructose (60 and 30 g) to increase resistance. Microvascular endothelial function did not differ in response to the ingestion of various sugary drinks. In conclusion, ingestion of fructose, but not sucrose, increases BP in healthy human subjects. Although sucrose comprises glucose and fructose, its changes in TPR and CO are more related to glucose than to fructose.The British journal of nutrition 04/2014; · 3.45 Impact Factor