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Physiological testing of a beverage system designed for long-haul air travel


Long-haul air travel imposes multiple stressors, arising from prolonged immobility, low humidity, modest hypobaria, circadian disruption and oxidative stress from food and cosmic radiation [1]. We developed a beverage system (Flyhidrate™ a) to counteract such effects, using ingredients shown in previous research to be effective when used acutely in achievable quantities, with low risk of adverse effects in unscreened populations. Flyhidrate is a 3*330 mL beverage system based on sodium-citrate and sodium-chloride for hydration, with supplemental ingredients (esp. fruit extracts) for early, mid and/or late phase flying effects. The aim of this study was to determine the physiological effectiveness of Flyhidrate in lab trials that simulated long-haul flying to the extent possible in our testing facilities.


In a double-blind, placebo-controlled, crossover design, 12 male adult volunteers (mean (SD): mass 76 (16) kg) underwent two 7-h trials, at least one week apart (both at 24.2 (0.1) °C, 30.4 (1.5)% rh). Participants were seated except for two 10-min periods used for micturition. In each trial, participants consumed a standardised snack, meal and normal fluids (430 mL water, tea and coffee; ad libitum in first trial, then repeated in second trial), and 330 mL of Flyhidrate or equal volumes of equivalently-coloured and flavoured placebo (143 kJ energy and 0.8 mMol sodium) at 0.3, 3.0 and 5.7 h (i.e., 990 mL of each beverage). Each Flyhidrate 330-mL drink, depending on its role, contains 298-913 mg polyphenols, 0-48 g caffeine, 255-288 kJ energy and 21.7 mMol sodium, and has an osmolality of 336-378 mOsmol/kg.


Urine output across 7 h was 0.23 ± 0.16 L (mean ± 95% CI; p = 0.02) lower in Flyhidrate than in Placebo (1.05 (0.48) vs. 1.28 (0.34) L). Approximately half (0.13 L) of this difference was evident after the first drink (p = 0.01). Total body water loss, assessed from bioimpedance analysis, was 0.4 ± 0.4 L less in Flyhidrate (p = 0.05), and plasma volume increased by 3.0 ± 2.8% (p = 0.04) more in Flyhidrate than in Placebo (4.1 vs 1.1%). Flyhidrate provided no clear effect on the seating-induced increase in calf girth (0.5 vs 1.3% p = 0.10) or ankle girth (0.2 vs 0.8%; p = 0.23). Effects on heart rate were similarly unclear (p = 0.70). Oxidative stress, as indicated from plasma concentration of Advanced Oxidative Protein Products, increased by 171% for Flyhidrate and 199% for Placebo, without measurable difference (p = 0.50).


Fluid balance and plasma volume were maintained more effectively with Flyhidrate than with a matched volume of placebo beverage, despite the consumption of other fluids. These findings concur with those from a field trial of another sodium-based beverage in long-haul flying [2]. Other potential physiological effects from supplemental ingredients were not discernible in these laboratory trials. Controlled trials involving a more complete representation of the stressors of long-haul air travel appear necessary to examine such effects.


The customised beverage system maintained fluid balance and plasma volume more effectively than did a placebo beverage, but other potential benefits were unclear in this setting.


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Acknowledgement and disclosure

The concept of this beverage system and funding for the study was provided by Flyhidrate Ltd, New Zealand. Thanks to Michael Dessoulavy for oxidative stress analyses.

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Correspondence to James D Cotter.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Cotter, J.D., Parr, E.B., Silcock, P. et al. Physiological testing of a beverage system designed for long-haul air travel. Extrem Physiol Med 4 (Suppl 1), A61 (2015).

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